Imagine if we had to download the Windows Store on iOS just to get Outlook, Word or Excel though. That's what the OP is predicting.
And yet that never happens on Android. All of the major players use Google play store because regular consumers aren't gonna install another app store just to use some apps.
Clearly Epic thinks they'll do it. Different ecosystem, who knows?
Sadly this comparison is very misleading. Steam was a thing for a decade before the windows store and it has been basically the default. The more game stores that appeared over time the worse it has been for the gamers.