I’m assuming it was a strategy to prevent easy trapping and griefing in the nether. Not sure if preventing it still serves a purpose but perhaps it’s still a risk
I don’t know whether there’s any further reason, but a similar thing is done with obsidian and lava to prevent mass farming. I know magma blocks can be crafted with 4 magma cream, so if you are desperate to have some for your island, that's your way around not being able to mine them.
Junezombee1 , magma blocks are easily obtainable at player stores. They sell for about 64 per grass or more. Contact me in game if you need only a few, I may have some left over.
Since the nether is infinite, there is theoretically an infinite amount of the materials available to be mined within the nether. To combat items from the nether having no value, items were divided into those that can be mined normally, those which have reduced drop rates, and those which you cannot mine at all. Normal Drop Rates: Netherrack - This block is quite literally infinite, and does not have much value. Most of it's value comes from being used as an infinite fire block, being used for terraforming, and being smelted into bricks for creating building blocks. Since it has very little value as itself, and it can only be obtained from the nether, it has normal drop rates. Reduced Drop Rates: Sould Sand - Only available from the nether, and has some value for netherwart farm purposes. Quartz Ore - Only available from the nether, and quartz is a popular building block, as well as the quartz pieces can be used for various redstone components. Its drop rate is set very low as to maintain some sort of value for it. Gravel - Only available from the nether, and has various uses, primarily for concrete production. Netherbrick Blocks/Fences - These can be obtained otherwise by smelting netherrack into bricks and then crafting into blocks. To give some value to being able to smelt instead of just mining fortresses, these drop rates are reduced. Glowstone - Can be obtained in the overworld by killing witches, either in a natural mob grinder, or at /warp hostile. Both of those processes can be very tedious, though, so glowstone is provided as an option to mine in the nether as well. It is given a reduced drop rate to help maintain value. Cannot Retrieve: Lava - Lava is overly abundant and truly infinite in the nether. If players were allowed to retrieve it, obsidian would have little to no value. Obsidian can be obtained otherwise from /warp trade or chests in fortresses. Magma Blocks - These are also quite abundant in the nether. The mining of this block is fully blocked as there are other methods of obtaining this block which help maintain the value. Players are able to kill magma cubes to obtain magma cream, then craft that into magma blocks. As farming magma cubes is fairly easy, it already gives magma cubes a relatively cheap price. Allowing players to mine magma blocks, even at a reduced drop rate, would further reduce the value. Overall, the system is balanced in such a way that there are only one or a few ways to obtain nether specific items. Reduced drop rates/preventing certain blocks from being mined is necessary to combat the infinity of resources the nether offers.
The Nether is not infinite, it's finite because If you travel over 30 million blocks away from 0, 0, You will see a unbreakable border, you also can't use ender pearls, minecarts, or liquid to bypass the border of Minecraft. This isn't only in the nether only, this is in the Overworld and The End. Well the materials in the Nether is finite, not Infinite, Nether materials from /warp grass is unlimited resources.
The nether itself is not literally infinite, no. When the nether is reset, however, like we currently do every month and previously every few months, it is essentially infinite.
No, you said the resources were limited because of the world border. But you can use Ender pearls, Minecarts, Boats and Chorus Fruit to go past the world border, but interacting with anything is buggy past it. Do all of the meterials in the nether, by every reset, get taken? No, there’s always at least 80 unlooted fortresses, enough unmined quartz to make the Taj ma Hal in Minecraft, and enough gravel to fill a 99x99x256. Not sure what your point is, the nether’s fine and you’re going off-topic to the thread (which is why Magma Blocks are unminable in the nether)
I’m not sure about the rules/status on this now, but at the beginning of last year zim1970 showed me how he took lava from the nether easily with dispensers and buckets. Was this patched?
This was patched on the Skyblock Survival server a decent while ago. I haven't tested on other servers to see if similar methods still work. Buckets, droppers, and dispensers are currently completely prevented from being used in the nether.
Not sure if you have read the rules, but lava is illegal to trade. As redstone and other have said the value of obsidian will go down and the number of accidents caused by players (accidentally falling and dropping items) will go high which will in turn cause a lot of players to whine about it in chat and put more strain on donors (cause they always trail us for free stuff). While it may increase demand for certain items, the overall effect will be very little to no change. Lets face it do you want a chat full of people whining about how they died and/or lost all their stuff or would you have a chat that talks about why Canada is better than the US? Also, griefing will go up because of lava's nature to destroy things.
Then they should be breakble but with 0% drop rate. I know the nether resets monthly and it's pointless to build there but having something that scattered literally everywhere and behave as unbreakable obstacles to players in a resource world that is supposed to be excavated isn't really a good mechanic TBH. Another reason is this is normal activity we all do in vanilla while exploring the nether so I don't see the point of them not being breakable while the server is vanilla-oriented, it's like random trap on terrain that can only be avoided and you can do nothing about it, not really a good trap just plain annoying. I've also noticed they can be used as bunker material in PVP situation, by simply use piston to rearrange them in a shape of a hollow box and using chorus fruit to get in but I doubt people would do such a boring thing just for a bunker that live for a month.