they should be prefixed with something human readable so you can tell a service bot api key from a human developer api key or whatever.

hahahaha as if humans wouldn't just give their hey to the bot

That misses the point. The point is for easy validation that the key was generated appropriately. Many api keys have a standard prefix for just this reason. It especially helps on documentation where the key name might be confused with the value: "your key starts with hnkey-"