You can always use the 1.12 recipe book instead of /recipe so I believe that's why they removed it if I'm correct. For the /calc you can always use the calculator hidden somewhere in your computer or your mind : ))
The 1.12 recipe book is much easier to use now, as Bert said. With the ability to create stuff straight from that menu makes /recipe redundant. I also doubt whether //calc was used that much by the majority of the players online. Most people don't know it exists or don't have a need for it. It's most likely been removed to reduce the amount of unneeded commands. If its something you'd like back, you can always make a suggestion thread!
//calc was removed because I talked to leeeroieee about there being a possibility to crash the server by trying to calculate an equation that is too much for the server processor. This is why it is removed. This equation could have an ability to crash the server: //calc for(i=0;i<256;i++){for(j=0;j<256;j++){for(k=0;k<256;k++){for(l=0;l<256;l++){ln(pi)}}}}
I'm mainly sure it was removed because it caused a major issue on the main server, need someone to correct me if I am wrong. I did use it from time to time, kinda useless but I did use it
They aren't really that important in my opinion. In 1.12, as stated above, you can use the recipe book for recipes and not many people used /calc so there was no need for it. You can always use the calculator on google.
So many people didn't even though that the //calc command existed, so I don't think that's a big issue really /recipe would be frustrating to not have anymore if it weren't for the 1.12 recipe book: I think that's really useful and possibly more convenient than /recipe was anyway