Kristian: Physical stores have limitations like shelf space, but that is not really the case with a store like GOG, so while the following might not always apply to physical stores, it should mostly apply to GOG: Profits from selling game A and game B > profits from selling only game A and not game B.
I will claim that many if not most games rejected by GOG would not have hurt their business or profits in anyway. On the contrary several would have helped them in that regard, some even significantly.
Edit:
Is Vigilantes shovelware? Would it hurt GOG's business to have it here?
We've had this argument dozens and dozens of times.
There are costs involved in GOG selling a game, they commit to testing and providing support for every game they sell (something which I don't think any other store does, certainly not the major players). So if GOG spends maybe a few thousand pounds on said testing and writing up legal agreements to sell a game, then a little marketing (sure, writing one release post is the extent of a lot of their marketing for games, but it's still a non zero cost), plus hosting costs, manpower to set up the game page and do any artwork required and only sells 100 copies at £5 then they have made a loss.
And looking at the popularity and best selling lists shows that lots of games which have been out a long time languish in the last few pages and obviously don't sell well. It's almost impossible to judge if they have sold 5, 50, 500 or 5000 copies but I think it's safe to say many games fall at the lower end of that scale, and hence make very little return for GOG.
So no, selling more games isn't always better and more profitable, not with GOG's model. And personally I'd rather they sold less tested, supported and curated games then dropping testing and support and selling anything and everything.