Given that it makes some sense to try to brand a particular presence in NY. A bit like how a fashion store might want to have a strong presence in Paris. And given NYC alone has a runrate of more than $300m alone, it's not strange to approach this as its own market, just like a company might have a US, UK, JP, DE etc domain for those country markets. Only Uber is more city-segmented than country-segmented right now, each city has its own taxi ecosystem and legislation.
In any case, it'd be an easy redirect and for a company worth tens of billions, outspending a $3k bid to get a branded domain for your company's largest market makes sense. Even if you don't use it, grabbing it and redirecting may be useful. Who knows if its worth much in the future.
So I wouldn't say that grabbing a uber.nyc domain name is the best move ever but it's not strange given the context. I'd have done it.