Because I am sympathetic to the idea that they offer a service paid for by ad revenue. If want the service, it has to be paid for somehow. I don't mind ignoring a few innocuous ads if it means the service remains "free."

yeah but that's the point: 'innocuous ads' have never been tested on the net.

it started as attention seeking eye-knifes, transitioned into the sex sells & hardcore gamer crap, and ended up as 'legal' reverse mortgages/fake charities/malware/data-harvesting.

I think it's safe to say that experiment has been tried.