Ad agencies generally use a variety of fee structures: https://yourbusiness.azcentral.com/advertising-agency-fee-st.... If you step back one level of abstraction, I'm not sure pay-per-click nets advertises more ad revenue than other billing models would, it's just an easy way to calculate things. And in the legal field, fixed fee or hybrid fee structures are very common. In practice, those options aren't cheaper than just negotiating for a discount on hourly rates; they just allocate the risks over/under-estimation differently.

Also, plaintiffs have huge incentives to move cases along quickly, because very often some or all of their compensation is tied to the outcome. But cases with contingency lawyers who aren't getting paid until the client gets paid don't move any more quickly than other kinds of cases.

As for why there are not more judges: what do you think of this proposal to create a whole bunch of new judgeships? https://thinkprogress.org/wp-content/uploads/2017/11/calabre....