[evercast]

Calling Uber just "a taxi app" is IMHO like calling Facebook just a website. Sure, that's what the end user gets, but there is plenty of engineering involved such as maps service (I believe they have their own, but I might be wrong), geo searching for locations, batch processing for data analytics, ML experiments etc.

I believe Uber is also well known for building everything in house as opposed to using common cloud services. So they need to run their stuff.