[duped]

I came over to Rust from C++ and I really don't want core Rust development to slowdown. The changes you see are mostly useful APIs in std.

Compare to C++, where using a new std API/type can take a literal decade and might not be backwards compatible on targets even once compiled.

Stability is only useful if it gets in the way of reliability and convenience. That's true in C/C++ because of the compilation and development model. In Rust those problems don't exist, so "stability" of std largely gets in the way.