I wouldn't have much reason not to buy from Epic, but I also wouldn't have any reason to buy from it either. Other than free games I don't see why pick Epic over any other place. Steam has more features and GOG is DRM-free, even ItchIO has the benefit of being more supportive of smaller and upcoming game devs. Epic doesn't do anything but the basic.

Tim Sweeney hates linux so that's why I prefer Steam over it. Even though Epic gives people free games, the games were always free anyway (unless you want multiplayer), I know you said piracy isn't an answer though.

Their exclusives , the anti linux stance and the store is crap too

The first major issue for me was that the launcher was a crypto miner and they didn't tell anyone.

Since then, I have 0 trust in them and refuse to install the launcher. I don't care for the "free games"

what’s the issue with Epic

Enshittification.

why should I go for Steam

Not sure you should.

or GoG?

I hear GoG tends to be less DRM-y.

Issues I can think of in the order they occur to me. These are off the top of my head refections not researched.

1. Group think: If I shop where most other people shop I have outsourced research and decision making. Is there a good reason? maybe, maybe not but I'm going to follow the masses because I can't research everything.

2. Stability: neither store offers physical assets so if the store shuts down my purchases could also vanish. Steam is a bigger player and appears to be more stable and GOG is DRM free.

3 The shopping experience: I personally find the layout of steam better for discovery and finding reviews. With the current epic coupon available I have looked on epic for games and if you're just browsing it is not a intuitive experience. GOG similarly has a variety of sorting tools available.

4. private vs public ownership: Epic is a public for profit company. Over and over I have seen public companies screw there customers in the interest of profit. Valve (I believe, this is really off the top of my head) is privately held and as such can choose to prioritize whatever their leadership wants. They can't just be bought out and taken in a totally different direction.

This all could be insane ramblings but these are the things that motivate me to spend my money on Gog or steam in general.

Epic client is a spyware.

I personally don't give a shit about whichever store I use for gaming because I have no loyalty to Steam like a lot of the people in this thread. It's just a store and launcher. I wish people would get a grip.

I buy games where it's cheapest, whether that's GoG, Steam or Epic or anywhere else. I use the wishlist functions to make sure I can price compare on sales etc.