The power of a software is in composing things via powerful abstractions. When you write a useful library in a PL with GC, you automatically make it unavailable in all applications that can't use GC. What's worse, other libraries that could've built something around yours have to choose whether to limit their applicability to applications with GC or find another way.

But if you have a clever language that navigates this tradeoff and lets you build powerful zero-cost abstractions (C++, Rust, Zig), then it attracts significantly more talent that compounds.