It's true that if they do something highly awful, then that might create enough demand for a competitor to take over. But it would have to be a high degree of awfulness to overcome their existing momentum. There are many shades of not-quite-awful, where those companies can make decisions with market impunity.
So considering that we're kinda stuck with those guys, I think the question becomes, why shouldn't we complain if they are doing something that we don't like? Doesn't matter who owes who what. It's our world, we should try to improve it.