I'm rather pessimistic about Uber's rationale for its pricing... and I'd just say they were greedy. Yes, companies like Uber have cost for churning/acquiring customers. This still doesn't explain why a driver only receives ~35-50% of the total paid. Also, at least in California, we pay an extra fee that supposedly goes direct to the driver.
FWIW, I know private drivers that don't work with Uber/Lyft or any other rideshare app, and they're great. Reasonable prices, always nice to know the driver, and great for pickups at LAX since they can meet me at the terminal rather than the rideshare pickup area.