Are you a pc gamer? Because if you are, I don't understand how you can't see Steam as a massive monopoly.
Perhaps you don't because they have done almost all GOOD with their monopoly power. Offline mode, library sharing, massive sales, etc.. but they are quite a monopoly.
If 99% of my library is on Steam, why should I bother buying somewhere else? It's just an inconvenience to me. Ok I can buy off GOG and have no DRM.... how does that really help me? I can already play it on steam with no problems, my friends can play the shared game on steam, I don't have to worry about multiple platforms etc..
Anyway- steam is a massive monopoly and we are lucky they use their powers for good!
Network effects make Steam a practical monopoly. And it's probably no coincidence it has lower rates for AAA studios since Epic has gained a foothold in the market.