We were talking about how I only do this once in a while when I have spare time, partly because it doesn't pay very well, and Uber routinely gives drivers a small fraction of what they charge the passenger. This one turned out to be a rare exception -- the trip netted $18 and change for me of the $25 and change they were charged. I think it's partly because I got an extra bit for "long pickup" time and distance, and the pet fee that must just go straight through, plus a small surge amount. They even added a tip after the ride!
Drivers get to decide whether they're open to Uber Pet, i.e. transporting people with their companion animals, but are required by law to take service animals, period. That just makes sense.