[mattmanser]

Because the position (and power) is symbolic and the centuries old understanding is that the ruling monarch will never exercise it. Should they do so, especially in opposition to a full referendum of all things, it would spell the end of the monarchy.

The last time royal assent was refused in the UK was in 1708:

https://en.wikipedia.org/wiki/Scottish_Militia_Bill

[Latteland]

What if the king or queen was a crazy bastard hell bent or just too stupid to do anything but destroy your normal democratic behaviors and support authoritarian practices? I think you've been lucky up to now, at least for the recent 100 years.