- If a publisher is considering two retailers, one who gives them a larger cut than the other, that publisher might prefer to sell through whichever gives them a better deal. That also gives the publisher a wider range of MSRP options on those products. That has potential value to buyers and the seller alike, even when short-term volume differences might seemingly obscure the difference.
- An entrenched retailer can have a variety of membership benefits that some consumers may not actually engage with. Those benefits can have concrete benefits in theory, but still be superfluous for many buyers. A publisher may not consider those exclusive retailer benefits key to their sales, especially if the overhead demanded from the retailer is dramatic compared to alternatives.
- A new retailer which demonstrably has a large, younger, and effectively exclusive market for their user-base compared to other retailers would find it easy to appeal to a publisher for timed exclusivity on a product if they're given good terms. The product as it pertains to end-users, in every way which the publisher can control, is the same whether sold at the newer retailer or any other.
- An entrenched retailer which has existed long enough to have a heavily competative selling space and less maleable policies/terms for publishers might be justification enough for some publishers to experiment with exclusivity in emerging retailers.
All of these and more are reasons why another store like Epic represent valid competition for Steam. This is an experiement, with very real incentives for the publisher. There are no guarantees for success, and every publisher is keenly aware of that, even when making the choice for an exclusivity window for their products. Steam has formulated and integrated industry-standard benefits for users and publishers alike, which is part of
why they have the well-earned mindshare that they do. Valve has been lockstep with the interests and demands of the market for longer than some people have been gaming. That should never be understated, but conversely, buyers petulantly ignoring business factors will just find themselves confused and irritated if they won't accept
any fledgling offering for a product from another retailer, even one from a company that predates Valve in game development. Insisting that basically any deviation is caustic to the market itself is a misguided attitude.
I'll still center my purchasing on Steam, but the suggestion (as in the OP/thread title) that there's no broader value to be had from a competitor like the Epic Store because they use exclusivity agreements is being myopic.