GOG is absolutely tiny. It was sold by CD Projekt to one of the store's founders for a mere $25 million last year:

https://screenrant.com/gog-sold-cd-projeckt-red-new-owner/

I know several family-owned businesses in my small town (that nobody outside of very specialized industries has ever heard of), which are worth significantly more each.

Profits were just $1.2 million in 2022:

https://www.pcgamer.com/software/platforms/wrestling-the-steam-goliath-pulling-a-nightdive-and-seeing-off-vulture-capital-gog-chats-the-risks-and-opportunities-of-its-future-as-a-company-without-cd-projekt/

Again, absolute peanuts compared to other online storefronts.

While the site does provide a highly valuable service, it's far too small, too little known and has been so for such a long time that I doubt it can grow significantly in the foreseeable future.