Why are there a limited amount of close votes for high rep users?

Question

I am a reasonable high rep user and have been around for some time now, and even though both of those are the case I still have a limited amount of close votes I can cast (40), why is this? Surely the system can trust me not to abuse my ability to cast them as I've been around for a while and have over 10k rep?
I think that when users reach something like 10k that their close vote limit should at least go up if not become unlimited. Perhaps you'd only want 20k users to get it unlimited, but I still don't see why there is a limit for me, aren't I trusted (I'm not suggesting that I shouldn't have a limit, and others should, just that people like me who have a reasonable amount of rep and have been around for a while should be more trusted with responsibly casting close votes)?
If the votes can't be unlimited, then at least they should increase with your rep, or maybe it should depend upon how many questions you've cast close votes on have actually been closed and also how many then reopened.