Not as much collusion as simply lack of competition.
You don’t have any other options for most of their respective platform and there isn’t enough incentive to compete on the pricing.
Also even when there is competition there are rules that prevent you from lowering pricing in one store vs the other (there are some exceptions) so if you end up say selling a game on the PC and you set the retail price as $60 and you launch it on 3 different digital content distribution platforms while you might make more money on one platform than the other there is no difference for the end consumer so there isn’t an actual competitive incentive to reduce your cut as a digital distributor unless you think you can get an exclusivity deal.
You don’t have any other options for most of their respective platform and there isn’t enough incentive to compete on the pricing.
Also even when there is competition there are rules that prevent you from lowering pricing in one store vs the other (there are some exceptions) so if you end up say selling a game on the PC and you set the retail price as $60 and you launch it on 3 different digital content distribution platforms while you might make more money on one platform than the other there is no difference for the end consumer so there isn’t an actual competitive incentive to reduce your cut as a digital distributor unless you think you can get an exclusivity deal.