Amp vs powered speaker confusion….

So, today I’m wondering why people spend a fortune on an amp when powered speakers don’t require a separate amp or do most people prefer passive speakers ?

For sound quality do you think the speakers are more important or the amp? I’m guessing both, provided you have the amp paired up with the right speakers. So, do you guys decide on speakers first then look for an amp or the other way around? So, if you already had speakers then the goal is to find the correct amp for those particular speakers or if a fantastic amp just came out would that make you sell your speakers then find a pair that matches that amp? All pretty complicated to me.