Well "regular functions" in the sense that these are methods of the primitive type u8†, and of course neither C nor C++ can do that at all. So, yeah, it's a language thing.

In C++ what you'd do here instead is invent custom types and add the methods you want to the types, and I would give C++ credit here if the stdlib provided say, a bunch-of-bits base type with all the bit-twiddling methods defined and maybe specialisations for the 32-bit and 8-bit unsigned integers or something, but AFAICT it doesn't do anything like that.

"I could go out of my way to do this" is true for everything in any of the general purpose languages by their nature.

† In Rust if we define a function associated to a type T with a "self" first parameter then you can call that function as just a method on any value of type T and the appropriate parameter is inferred. So e.g. u8::checked_sub(u8::MAX, 10) is Some(245) but u8::MAX.checked_sub(10) is also Some(245) because it de-sugars to the same call.