No name mangling by default, far simpler toolchain, no dependence on libstdc++, compiles faster, usable with TCC/chibicc (i.e. much more amenable to custom tooling, be it at the level of a lexer, parser, or full compiler).

C’s simplicity can be frustrating, but it’s an extremely hackable language thanks to that simplicity. Once you opt in to C++, even nominally, you lose that.