Can’t they? Why not? There is nothing wrong with having more competition, especially if that competition can reduce prices for consumers and increase revenue for developers.
You talk about features, but in the end, only two things are important.
1). Is it available?
2). Does it fit my budget?
If I have a PC, and the game is on Epic, the game is available. There barrier to entry is not a new PC or console, it’s not a subscription. It’s a webstore.
And if it’s available, I will buy it when the game fits my budget. So, if it goes on sale on Epic first or sold cheaper on Epic, that’s where I am going to buy it.
The rest is just mumbo jumbo sales crap. Like a moon roof on a car. Sure, it’s neat, but if it’s too pricy, I don’t care about the moon roof. If the care doesn’t run, I don’t care about the moon roof.
In the end, we are talking about a completely elastic commodity, and in those cases, the market will decide.
In the meantime, I am in favor of having more markets available in the long term, which means robust independent stores that aren’t reliant on Steam’s largesse.
I have seen companies rely on YouTube, or Facebook, or Amazon, and when the terms of service change, or when something profitable occurs, they get wrecked by the very platform they rely on (especially on Amazon). So, you will forgive me if I don’t trust the long term viability of Greenman Gaming, or Gamergate, or fanatical, and would prefer to have more services compete directly with Steam.