Uber has to do all kinds of things that a taxi company wouldn't need to do. For example they have an entire department related to resolving sexual assault/harassment issues between customers and drivers. A taxi company would just send the the matter to the police and be done with it.
They also must have a large "compliance" department as each city, state and country seems to be enacting a different set of rules around how the company can operate.
All these different departments need software to support them (no point in having compliance if the app forgets to charge the right tax somewhere!), which means they need more accountants, more HR people, etc.
It seems like Uber could trim some fat (I had an interview with them that was laughably easy), but who knows if the CEO thinks he can do that without causing low morale and a stampede of the actual talent.
