Posted 14 April 2014 - 05:26 AM
Here's plenty of rivals, but steam got in first and carved out a huge chunk of market-share for themselves. Things like steam chat, gifting, trade, forums, etc connect their users, so that they don't want to switch to other services. They also offer a lot of services to devs, such as the obvious file hosting and (very fast, global) distribution, patching, public/private betas, branches, micropayment API, VOIP APIs, NAT punch-through with free proxy fallbacks, matchmaking, lobbies, etc... On top of that, they've (seemingly?) got the majority of digital PC consumers on the hook, making their store a place you really want to be available from.
All this makes for a very strong feedback loop, keeping it the dominant force.
EA, Ubisoft and the smaller 'indie' versions don't even have feature parity... Along with having less consumers visiting them. Some of the indie ones are much more user friendly, such as having no DRM, or letting you use them without an account, but are competing as niche operators, rather than actual mainstream competition.