- Keeping your pc free of malware. - Keeping people from trying to aggressively promote lies, half truths, and nonsense in your own home. - Making the web work both better and faster.
From my own experience (I did various research projects on this working with journalists) the data usually ends up in places where it's not supposed to be and might cause a lot of harm in the future, hence by blocking this content I'm trying to protect myself as good as I can.
I'd accept ads if the following conditions are met:
* They are served through a trustworthy CDN, which guarantees that my IP information will not leak to the ad network operator.
* They do not execute JS and consist of elements whose safety can be (reasonably) proved, e.g. images and text.
* They do not blink, move, break the page or hide the content that I want to read.
* They do not try to "contact the mothership", sending back personally identifiable information to their overlords.
Sadly, I have not seen a single serious effort to implement this, instead websites just ask me to disable my ad blocker and expose myself to privacy risks. No.