On my employee orientation a few years ago, we were shown charts from the finances team with breakdown of gross income vs the various cost centers and they were talking about how established cities were profitable and new cities were not due to various reasons (see my other comment downthread)
My personal take on this is that eventually the world will run out of cities for Uber to expand into and every city will either be profitable or deemed not worth entering.
I don't really buy the argument that any fat slob willing to burn money can displace Uber in an established market in any significant way. The stealing marketshare strategy only works while all parties are still growing in a given market. Once the growth stops, it's a race to the bottom, and I don't think any investor wants that.
Uber has a lot more leeway in how it can reallocate resources if one local competitor decides to spring up in some random market, just from its sheer scale, and at some point, the law of diminishing returns will probably make it not worth for someone else to try to be the third or fourth competitor in a given market.
At that point, if I were investing, I'd be pressuring those companies to either partner up, be acquired or cut some sort of exclusivity deal, giving Uber a share of profits.
And from history, that's exactly what has been happening. Uber left China by cutting a deal to take a cut of the pie, it partnered in Russia, and now there's the rumour about the Careem deal.