If you want bad service (long wait times, high prices) then your argument makes sense. However, the more people that use Uber will lead to better service levels and lower prices. Drivers benefit by minimizing wait times and being able to depend on the money.
And if you went to London, you get the convenience of not having to download a local app. You simply use Uber (what you're used to, what you depend on, what you trust), and you have one less thing to worry about in your travels.