“What keeps a new company like Goober from starting up tomorrow and offering the exact same services as Uber for a much lower price?”
Nothing. If you have the means to create the smart app, market it, and comply with various regulations, you can do it.
There is an innate advantage to being first to market though. Makes it difficult for competitors that come late to the game. But first in does not guarantee a win. Look at Yahoo and Google in the search engine wars. But also look at Bing. Once Google established itself as the defacto leader, even Microsoft could not cut much into its market share.
Uber now has a huge advantage with brand recognition, maps, logistics, a massive existing customer and contractor database, and lots of market research. They have tried many experiments, and know what works and what does not. They are way ahead of the competition.
On the flip side, big companies like Google, Tesla, or even car manufacturers may jump into the fray once self-driving cars become a thing. The cost of the driver is the number one expense for ride sharing. Self-driving cars will be more disruptive than ride sharing ever was.
The days of making money as a driver for Uber are numbered.
I agree with everything you've said about the advantages of being the first to market. The problem with an app-based product is that the cost of entry is very low -- and there's always going to be someone who can come up with some new sales pitch to drivers and customers alike.
I suspect there are few entrants in that market because everybody sees that it is not a profitable enterprise in the long run.
Ok, lets assume self driving cars become a reality soon. The ride sharing companies are going to need depots to fuel, clean and do maintenance on the cars. That all requires expensive infrastructure and people to do it. And with no supervision in the car, I suspect there would be considerable more cleaning envolved