Driver's who have done this gig for more than a few months (i.e. not many) know to just pass on passengers with low ratings. I won't pick up anything below a 4.7 myself and that seems to be more or less the cut-off for other drivers as well. Not everyone with a low rating is awful however **most** low-rated passengers are. Furthermore you take a huge ratings hit with low rated passengers as they tend to downrate vastly more as well - so it's just not worth it anyplace where there are a reasonable number of rides available. With that said, new drivers and desperate drivers (usually undoced immigrants who can't get any other job) will take so what low-rated passengers tend to experience is both longer wait times (as the ping bounces around to several drivers until one finally accepts it) and a lowered quality of service as experience, knowledgeable drivers refuse the rides.
Anyone who has worked in customer service for any length of time knows how that kind of job will ruin your entire faith in humanity. The difference with Uber is that when a passenger acts out (spilling drinks, eating in your car, doing makeup, you don't even want to know what else) it's YOUR car they are messing up - not some company car. I've had passengers come to my car, see my USB adapter by their feet (used for my video cam and Uber phone) and try to just tear out the wiring to charge their phones (GTFO!) without so much as a "May I?" You all will hate on me for this but college kids are the *worst* when it comes to common curtesy and a bit of simple respect. I totally get that we usually haven;t socially matured until we're past undergrad age but I don't want that kind of hassle myself so I avoid college pickups too.
Uber puts all the risk on the driver and now takes a full 50% (or more) of passenger payments (2 years ago it was 20%) - so much or most of the profit here is now going to Uber instead of the workers. Drivers are fed up and frankly I think this is "new policy" is just some social media whitewash and won't be effectively enforced.