System wide ad blockers can’t block a lot of ads, namely same-domain ads or those that are built into the html. Much rarer than the external page kind (DNS ones) thankfully.

I don’t think you need to with either a professional or enterpriese account (I think professional). Do need to with a home account though which is extremely annoying.

Libraries are ethical because they pay for the books. If we’re limited to only physical books, then they buy new ones every ~8-12 rentals. Additionally (though I couldn’t verify this through a search), I’ve heard they also pay more to buy them.