[Richpur]

In england at least the monarch has the power to do just about anything, they just wouldn't last long if they tried to do it without good reason - ultimately if parliament gets too far out of line (such as being a rubber stamp process for a group of people making decisions on a couch maybe?) she can summarily dissolve it. There have also been several times when the queen has sent laws back to be looked at again instead of signing off on them. So the power still is there, it's just not overtly used much.

In the end a hereditary sovereign spends their lives being prepared for the position - an elected one spends their lives learning how to con people into voting for them.