Uber grew quickly because of a savvy marketing ploy- appeal to people to get what they perceive as quick and easy money. Uber is essentially a variation on the "make 1000 dollars a day working from home" marketing ploy.
They shift all the risk to their "partners" and skirt regulations and requirements because "Uber" is just a dispatch service ( their contention).
They have grown so rapidly because tech dependent millennials use their phones for everything and as far as the consumer is concerned, it is "cool" and "easy".
I am waiting. The lawsuits are just starting to roll in. Most Uber "partners" have yet to deal with the 1099 tax hassle. Lawyers always go for "deep pockets" so lawyers are already trying to find ways to hold Uber accountable for the actions of its "partners". "Partners" are already suing because under the laws of many states they are employees and are entitled to employee benefits from Uber.
Uber has hit it's zenith, municipalities are already starting to adapt their regulations to have Uber,Lyft, and all "sharing" type Aps included.
Uber has made their boatload of cash. When it starts to look like they will lose the lawsuits or become subject to industry rules and regulations, I look for them to fold up their tent and go.
That's the name of the game. Make your money fast and get out when it looks like the tide is turning, then go on to something else.