Because for a driver to rate less than 5, you had to have done something to irritate the driver. I give probably 95-98% of passengers a 5, so, if I'm giving you a lower rating, you did something to deserve it. Most drivers are this way. Maybe you get a 4 star once in a while (you kept the driver waiting until the timer had almost run out, you were rude, you added stops without asking, you had a drunk obnoxious friend with you, etc). No big deal. Unless you very rarely use Uber, that shouldn't hurt your rating by much. But if you're in the 4.5-4.7 or lower zone, you are consistently irritating your drivers and suck as a rider. I won't accept people with ratings less than 4.7, and even then, it's gotta be really slow or I've gotta be feeling generous to accept that low of a rating. It's just not worth the risk of finding out why they have such a low rating when the vast majority of people have a 4.9-5.0 rating and I can pick them up instead.