Nobody is asking specifically if the majority of users want to specifically install the play store on their phones so answering a question nobody asked in the first place isn't terribly relevant.
The question is if the way Apple controlled the market fell afoul of legal standards in a way that effected makers and users. If this is deemed so it would be true regardless of what percentage of users would install apps from a third party store.
You're begging the question. Whether Apple in fact controls the market is the key point of contention here. If the company is simply responding to market demand then there is no credible theory of harm. I don't have any hard data but anecdotal evidences indicate people want more curation of apps, not less.
