DRM agnostic store is a fail of everything DRM-free community and GOG stands for. Imagine newspaper article titles: 100% DRM-Free store GOG starts selling games with DRM, DRM-Free business model is a failure, etc.
Going DRM-agnostic store would be an open treachery of DRM-Free cause, and destruction of store's own niche. What's GOG without DRM-free stance? A brand with no real values behind it?
I'll reiterate my past point here, but GOG is a corporation with clear profit-driven responsibilities to investors, not a movement.
Its not like you and me. It doesn't have morals. At this point, its an automaton that makes money for shareholders. I don't hold it liable to higher principles.
I however hold them accountable to an implicit agreement that was made when I handed over my dollars regarding every single game I purchased so far (with regard to sneaking drm in, I purchased these games drm-free and I expect them to stay that way right until the moment the store goes offline).
And regarding future purchases, I expect them to respect my values and not make it a mazelike experience to get the games I want. If they can't manage that, no point in giving them my money right? I don't intend to make every game I purchase a research work into exactly how much drm I'm getting.
GOG is clearly not a movement. But it's a big and integral part of video game and PC market history. Steam and GOG were two storefronts that raised PC market out of DRM war ashes of 00s, when every newspaper been chanting that PC gaming is dead, 95% of PC users are pirates, yada, yada. Those stores provided solutions to existing problems, and proved on practice that it works. It's Steam and GOG, who were the main driving force that formed modern PC market and created modern indie market. Made them big and highly profitable.
It's CD Project Red, who made a best, classical PC only CRPG of late 00s, and sold millions of copies on supposedly "dead" PC.
Those efforts are remembered and respected by PC gaming community, which is millions of people. It's not a small thing, because rarely corporations have this kind of reputation, respect and support by their customers.
And other people who answered you are right - shareholders definitely won't be happy. If company's reputation, market niche and advantage, that were built over more than a decade would be ruined by rushed and imprudent actions of GOG store's management. For breaking things is easy, while restore ruined requires hard work.