It's a more pragmatic design, for sure. I have some cool ideas for irregular sizes like UInt192 and UInt384, but it turns out that powers-of-two are still the kings of binary. There's not that much performance to squeeze out in between doubled widths, and any and every drop of it is paid in code size (although there might be some overlap for tripled widths). In the case of oddly sized bit patterns, it's probably™ better to extend them. At least, that's my hot take on it.