Well sending bytes and creating them costs money. Someone has to pay them. So it is either ads or payments. The money it costs are close to zero, so we need a way to pay close to zero, that is easy if we don't want ads.
Thank you for concisely expressing the core justification for micropayments. I have many arguments for why it's possible to implement, but I've never found a good way to describe why it's necessary before.
Maybe we'll get something from Mozilla eventually - but I'm not holding my breath. I suspect it'll only happen if there's a massive awareness campaign that produces a demand signal for it in the general public (as opposed to just tech nerds).