The problem is that many extant APIs return 64-bit integers, so if your language only has 56-bit integers you are creating a bug/vulnerability every time you want to talk to the outside world.

e.g. sqlite has sqlite3_column_int64() to get a value from a result set. How do you use that safely if your language can only do 56-bit ints? Ugly.

Remember the "Twitter Apocalypse" when Twitter changed their tweet IDs to be bigger than 56-bits and all the JS programmers had to switch to using strings?

Also, bitboards. Bitboards are cool: https://chessprogramming.wikispaces.com/Bitboards.

EDIT: I also reject the premise that just because there's an ugly hack available, we can get rid of useful language features. Am I working for the language or is the language working for me?

I have never ever thougt that float/double/decimal was too much choice.