Lack of persistence is one such reason. Because Go's built-in maps are not completely safe to use concurrently, too, their usefulness as a key/value store is somewhat limited in many applications.

Naturally, it's possible to build a solution to persist Go maps and to make them safe to access across goroutines, but by that point you've built a persistent key/value store.

Depends on the requirements (persistency, concurrency etc.) No offense, but it's bit pointless to discuss it further without deeper context.