[mac01021]

Most dynamic language implementations don't let me inline a bunch of 128-bit or 256-bit values in an array, or allocate them on the stack.

Code that deals with a lot of values which are small but larger than a machine word can be made a lot more efficient if there is a way to treat those values as not objects.

[slavapestov]

That is true, but the original poster was talking about heap allocation of simple integers, not larger values.