Largely the first mover advantage, I think. I'm sure once someone does it it'll be a (or it already is) a gold-rush, but the first to get to the finish line will realize the most gains initially.

I'm also not sure how relevant it is, but Uber has been successful in branding. It's not, "I'm going to ride share to the airport", it's usually, "I'm going to Uber to the airport."

But in the end - I have no idea :). It'll be interesting to see what happens!