As a consumer, I want the most for my buck. The topic of exclusivity is important to me for a variety of reasons, a major component of which is whether or not the platform a game is exclusive to is worth the hassle.
Disclaimer: I hated being forced to use Steam back in the day, I hated how games on PC suddenly became reliant on a specific digital platform. I'm a PC gamer because I enjoy the open-ended world of PCs; the ability to build my own system, customize it how I like, and to use it as I see fit. So when you constrain me to a digital platform, forcing me to become beholden to it, it grates on me.
Steam has, admittedly, grown since its initial release and is no longer an obnoxious bloatware on my system. It has many features that make it a world of its own. It has ways to build communities, to communicate with developers, to share gameplay with others, etc. etc. etc. Other people have already said as much and more. It no longer grates on me in the way it once did, but my chief concern will always be whether or not Steam will someday end up shutting down and leaving me without access to products I've paid for to enjoy from now till I'm buried.
That's why I like GOG as a platform, personally, because no matter what happens, those DRM-free games will, in some form of fashion, survive long after GOG ceases to exist (barring giant EMP blasts or the sudden extinction of humanity and whatnot). Compared with my massive Steam library, my GOG library still comes out ahead in numbers of games I've purchased over the years (many I've willingly double-purchased on both said platforms, to support the developers and the GOG platform in particular), and will always be the first place I look to for new (or good old) games.
Epic, by comparison, still has nothing to offer me as a consumer. Sure, they keep giving out free games that I already have on two or more digital platforms I use, but that isn't enough to convert me over. The only real benefit is to getting some exclusive, or limited-time exclusive games only currently available on their Epic digital platform. In nearly every other way, it lacks or is completely backwards (years behind, even) on features that are and have been standard on its rivals, Steam or otherwise. Beyond that, there are multiple issues others have with Epic's digital platform, such as whether people's private information is secure, their heavy ties with China-owned Tencent, etc., but I consider these to be icing on the cake compared with the overall lack of user-friendly features.
I understand that, for struggling developers and major publishers who like to see additional dollar signs, getting an exclusive contract offered to them by Epic with a large, undisclosed amount of money to help keep them afloat or flush is tempting and beneficial. But for me, as a consumer, this doesn't exactly translate to me in such a way that makes it beneficial for me to spend money on the Epic digital platform itself. At best, I can wait for them to work out the bugs and release former exclusives on my preferred platforms, especially after seeing how other consumers receive and report on the games. I can also save money by waiting for sales on my preferred platforms after the fact, if I decide to spend money on them at all.
The Everspace developers, in particular, noted that there is a growing distrust between consumers and developers/publishers in regards to several noteworthy events where Epic has, quite literally, swept games out from under other digital platforms despite promises made to release on them years ahead of time. Who wants to back a kickstarter project, for instance, when they aren't sure if the people running it aren't going to go back on their word near the end on important promises made from the get-go? Consumers like their choices, and they have their personal preferences. Promising one thing and providing something else entirely isn't the fastest way to earn consumer trust.
The Everspace developers know how important trust is between them and their fanbase, as well as others interested in their games, and want to ensure their public image remains trustworthy. It's hard to earn money from everyday consumers if they don't trust the makers of the product. They want people, particularly the ones who have already spent money on them, to believe them when they say the game will, in this instance, be available on final release for Steam, GOG, and Epic. It would not be a fun ordeal for Steam and GOG users to find out later down the road that, instead, the game will suddenly only be available on Epic for an indeterminate period of time, especially if they don't want to use the Epic platform in the first place.
In the end, if there are people who want to use Epic or don't care either way and get their games on Epic's platform, that is their consumer choice. But I feel there are better ways of handling the issue than by pulling fast ones on people who have spent money with the expectation that they're getting something specific when they're not. There's more than a few good reasons why I no longer back just any old kickstarter project that tickles my interest (ugh, The Mandate!), and the same goes for pre-orders and even sales. I'm much more careful as a result of past mishandlings.
It remains to be seen if Everspace 2 will truly succeed expectations, but they pulled it off once, so that's something worthwhile to note, and I have no reason to distrust their word and promises for the time being. So they get my backing, and possibly multiple purchases of their game and DLC on alternate platforms if I like what I see later down the line.
Apologies for the wall of text, but that's all I've got to say on that particular subject.
Edit: And I want to add that I'm not singling out any developers who have taken the Epic deal when offered to them, but rather I'm critical of the ones who made promises to be on GOG, Steam, etc. and suddenly reneged on said promises after it was taken for granted. Developers have to do what they have to do to stay afloat, but it shouldn't be at the expense of their consumer base, who are ultimately the ones who might be buying their products to help pay the bills down the line.