We're talking about end users, because openly admitting that end users are objects in the trade between companies risk opening a bigger can of worms.
> As far as end-users are concerned, there absolutely are alternatives: Bing and DuckDuckGo.
First, it's like choosing between two communication providers, both of which know there is no other choice and silently split market between them. I think a good idea would be to look at 20+% of market with suspicion, and act accordingly. Give me at least 5 - and in practice, more - options to choose, made so that it's nearly impossible for them to cooperate - then we can talk about freedom of choice.
Second, having alternative doesn't create a non-monopoly. If AMD had a smaller market share, Intel would be in much hotter water as recently as a decade ago. Google maintains share by a variety of ways, including app store, mobile OS, agreements for pre-installation etc. - all different actions aimed at maintaining the lead. Microsoft worked this way in around 1990-s, even though technically not only they wrote software.
This is an opinion.