Coca Cola sells water with flavouring and quite astonishing amounts of sugar. Apple sells nice devices made by what might as well be slave labour.
Both are propped up - actually maintained - by huge and vastly expensive brand management strategies.
The criticisms of individual campaigns here are missing the point. It's not about micro ad spend, but the perception of value and manipulation of behaviour created by the combined effect of multiple PR and advertising efforts - which include traditional print and TV/radio ad campaigns, guided advertorials disguised as news in the MSM, interviews with prominent figures, political campaigns of more or less obvious relevance to the core business activity, state, national, and international political lobbying, direct political campaign donations, advertorials masquerading as "freelance" journalism and blogging, managed astroturfing on social media, shareholder relationship management, product placements in movies and music promo videos, articles about commercial visual design elements in trade journals. And on and on.
That perception of value is - unsurprisingly - extremely valuable. And it's very much a US way of doing business. Instead of producing products that are inherently superior, produce something that is functional but glossily packaged, brand it as a premium lifestyle commodity, and charge exorbitant prices for it.,
The prices are traditionally far out of proportion to its actual utility. In fact real utility may well be negative - see also diabetes and any number of other health issues, depression associated with social media use, debt-driven spending on lifestyle products. Etc.
So the rent seeking comes from a kind of cultural squatting. There is value in dominating discourse in all of these different ways, because discourse and narrative define markets and ultimately control behaviour. And while this is happening other kinds of discourse - which may well have more real utility - are diminished at best and crowded out at worst.
So in this case it doesn't matter if Uber "wasted" their money. Uber have their own branding thing going, and explicit ad spend is a tiny part of that.
And even if all online ad spending ended tomorrow, a small number of corporations would have a difficult time for a while, but the marketing industry as a whole would inevitably interpret the change as minor damage and route around it.