Timboli: There is some contradiction there.
If it isn't about DRM, then why do so many of the game providers use it? Especially if as you say, their games get copied anyway.
A game isn't born with DRM. DRM is an added extra that costs. And clearly that cost is passed on.
I do agree there is more effort though, maintaining two versions of a game, DRM and DRM-Free, especially as many games get rushed to market, and in that process suffer cost savings, resulting in bugs and incompleteness ... or lesser completeness, things not done as well as they should be. Hell, I am surprised we get as many Linux and Mac versions as there is, as they would be a cost saving cut too. Factor in the cost of bugfixes and updates for two versions of a game, and the deterrents increase.
And yes, less functionality in some cases so the game can be DRM-Free. That wouldn't be a particularly encouraging factor to make a game DRM-Free.
DRM-Free is a continuing hard ask, especially in this age of increasing DRM.
GOG have been playing the survival game, which wasn't too hard in the beginning, because they had a good lot of AAA games that had become old games, but the greater portion of those that remain now, that aren't here, are in most cases mired in licensing and or ownership issues. Sure we have games becoming old games every year, but where once GOG was the store for old games, many owners and other stores have now seen the viability of selling old games, thanks to GOG's example. And of course a number of companies have now popped up that revitalize old games, rework or remaster and even remake them. Thus GOG need to continually think outside the box to keep surviving. Whether that will eventually mean compromises (or more of them), remains to be seen.
Of course, while this has been happening, Indie Games have improved in numbers, and in leaps and strides for a good number when it comes to better quality. In fact, Indie games have become a kind of acceptable norm. The advent of Kickstarter has also helped change the state of things.
Nothing stays the same. Changes keep marching on in the name of progress, and adaptions and compromises continually need to be made.
Remember that some DRM isn't just DRM, and in fact has function. For instance, using Steam DRM allows access to several community functions, including achievements. In many cases, the DRM is added to add the functions. So many of the "DRM" games on other platforms have DRM only to take advantage of functions that many users want. It is indeed a losing battle I think that GOG is fighting, (or even we as users are fighting) since DRM is in virtually everything. Your PC, your car, your phone... The manufacturer maintains more control than ever over the things you've been sold. And people love them for it for the "features" provided, the bonuses, the security, the assistance, the convenience.