The logic for street hails is that it's fundamentally impossible to negotiate prices or quality of service ahead of time. Enforcing a uniform price & service standard lends predictability to the procedure.
- How much for taking me from here to <Place X>?
- That would be $40.
- Alright, let's go.
If you were feeling more adventurous, you could opt for a small(er) provider without an established reputation, but it would cost a bit less than Toober. Most likely, there would be no problem.