Most long term Steam users know its quirks by now, but if both Steam and Epic games store were launched today, in their current state, Steam would struggle to get traction.
The reviews interface is just links to other websites with little aggregate data. The library does this thing where it greys out uninstalled games making it really hard to identify them. It crashes a lot. The social features aren't as well developed.
Steam's not perfect but it's surely superior. Though I would gladly pay for a game on epic over steam if only because epic has given me so much great shit
Enter the Gungeon, Control, Nioh, Alien Isolation, Darkest Dungeon, Europa, etc.
And you probably won't hear from them about their experience. And that might cause you to wonder why.