[kevb]

1 star (and 5 star) are always going to be the biggest buckets. Even if you try to be very fair and strict, what does a driver that doesn't show up get? 1 star. What about a driver that stabs you? 1 star. Crashes? 1 star. Gets lost and makes you late? 1 star. Smells bad and a bit rude, but gets you there on time? Maybe this is finally 2 stars. These are all bad, but getting stabbed is a lot worse than not showing up or getting lost.

Likewise for 5 stars. Friendly, safe, on time, gives you a cold bottle of water, have a nice conversation. 4 or 5 stars. Chases you down with the bag you forgot in his car? 5 stars. You fall in love and get married? 5 stars.