Their "taxi" business model was completely unsustainable. A moonshot was/is the only thing that'd save them. That's why they did this (the self-driving part we know for sure, and the alleged stuff, if proven).
Dispatch via app is a solid improvement over the old phonecalls or street pickup, automatic credit card billing is an improvement over cash, and in cities with shady taxi drivers, GPS tracking is an improvement over potentially hacked taxi meters.
So there is an obviously valuable business model for "taxi dispatch app" here even without a moonshot - just perhaps smaller than Uber's dream of being the only provider of personal transportation in the world.
Uber would need to start understanding how ordering of goods works, returns, and service/quality complaints.
They could do it, but there are a whole lot of domain specific problems and approaches to resolve and it's not clear that's it's long-term viable.
It's also the easiest part to copy, most taxi companies have already. Now try asking they investors why the spent so many billions of dollars to break into the taxi business?