they used to be in power, before church and state separated.
its really just an ego thing. Imagine having the title of King <insert your name> or Queen, etc etc. Royalty is usually associated with wealth, and wealth is generally 'power', therefor you are powerful. But these days the monarchy is just like any other brit out there. Only the King/Queen has ties to commonwealth countries through their constitutions(ie. australia).
it'd be a pain in the arse to be royalty, you'd be getting harrassed all the time. have to act a certain way...fuck that, lmao. its kinda like politics, when something bad happens somewhere, you have to go tour it and 'talk to the people'. it might be my anxiety speaking but having to go out and talk to random people about crap i probly dont even care about would be repulsive. kinda like wen Julia Gillard(the Aus pm) went and toured some of japan because of the tsunamis etc. she looked like such a dick from my point of view. politicians are just like preachers, they're all actors :P