While it's true that the Epic Store isn't good right now, at least they have a visible plan for improving it (with most features implemented within the next 6 months if the roadmap is to be believed).

And I definitely get why they buy exclusivity, even if it's timed. Let's face it, even if the epic store was already better than Steam, most people would still ignore it if it wasn't for exclusives. People are stubborn and lazy, they stick to what they know.
Just look at GOG, better than Steam but they don't even put a dent in Steam's profits, simply because Steam already got its massive comfy spot before any competition got to the scene.

Basically, to move into the marketplace and not fail, you need something that "forces" (not really because they can choose not to get the game, but you know what I mean) people to start using the Epic Launcher, and consoles have proven that exclusives work.