Major public transport lines are decided based on how people travel. It would be safe to say that a well designed system would cater to 80% of the distance I travel on any given day. That leaves 20% for ride sharing if I don't feel like walking for 15 minutes.

So I purchased a nice toyota for about $15,000 about 4 years back. 600 miles per month, 25 mpg, about $100 on gas every month, about $1200 every year. Assuming that I use this car for another year, I paid out $3000 for every year + $1200 on gas=$4200 /year (I'm sure my car will last far more than 5 years). Uber is about a dollar per mile. So every month I would have to pay $600, every year about $7200. You could try and hook me up with another person traveling the exact same route, but that is going to be a very uncertain thing even if you have the relevant technology. Even a small degree of uncertainty will lead me to buy a car.

Now if I used public transport, I would pay less than $1000/year. Plus, there wouldn't be much uncertainty. I think the world would be a much more efficient place if we tried to make the $1000 ride more convenient/efficient, than if we tried to bring down the cost of a $7200 ride (although I hope they can do it, would love to see how they do it).

I never said ride sharing is all doom and gloom, I'm just saying it will have a smaller space in terms of number of people traveling.