I accidentally watched a YouTube video on a browser without blocking. It started with an ad. I thought I'd just endure it this time. Then another ad. OK, just this time then. Suddenly, another ad in the middle of the video. I gave up. Who'd have the patience to sit through this?
Then there's Google's habit of completely ignoring the browser's language settings so I have to sit though ads I don't even understand.
I don't know any other search that lets you block urls from results. Blocking stuff like social media and Amazon cleans up the results very well.