Many people don't need generics? Significant runtime cost? I would argue that everyone should be using type-safe collections like maps, lists, etc. (I know these are built into the language in Go, but they're basically special-cased generics). And, if anything, not having generics has more cost because you end up boxing your values to place into collections rather than letting the compiler monomorphize it. The compilation cost can be more expensive, yes, but it saves a lot of work you would be doing by hand.
While Go has had generics for a while now, the vast swath of existing Go code doesn't. The situation is definitely improving but there is still a lot of non-generic legacy cruft.
While Go has had generics for a while now, the vast swath of existing Go code doesn't. The situation is definitely improving but there is still a lot of non-generic legacy cruft.