The last straw, for me, was to discover that XCOM 2 is available for Mac if I had bought it from Steam; I use a Mac for work and having games on it means I can play them when on work assignments away from my gaming desktop. XCOM 2 is not available for Mac on the GOG version.

I know some people will reply that it's the developer's decision (in fact that is indeed the case here), or some other reason. As a consumer, I don't care one iota about that - the fact remains that XCOM 2 on Steam works on my Mac, and XCOM 2 on GOG doesn't.

Another factor is the Steam Workshop, which for some games makes modding so incredibly easier. This is compounded by mods generally being thought for Windows (understandable; modders work for free, so they target their own platform), but if they use Steam Workshop, mods generally work on Mac as well. Rimworld is a good example of this, and I ended up buying the base game again on Steam, plus all the DLCs on Steam, just to have an easier time modding it.

For this reason, from now on I'll buy on Steam whenever possible, and GOG will be second choice. The annoyance of DRM is largely compensated by more games available on my work machine and better modding support. Until now, this was reversed, and I'd buy on Steam only if GOG was not possible or was significantly more expensive.

I really hope GOG sorts itself out, because even if Steam is better at the moment, it's beneficial to have multiple options, but right now I can't see GOG competing.

Yea, I also hope publishers and developers and modders sort themselves out.

It's almost as though the bigger store has the resources to support the non-Windows operating systems better than the smaller store does. That said, it's my opinion that GOG wastes their resources pushing Galaxy. However, it's still worth supporting DRM-free gaming..."muh convenience" is why the PC gaming market is a DRMed cesspool, so thanks OP for adding some more waste to it by supporting Scheme.