It probably won’t surprise you to hear that distributing RPGs can be a major pain, especially for independent publishers. Printing physical copies, funding shipping and distribution, dealing with returns, controlling PDF disbursement, combating pirates—the list of issues goes on. Some authors have chosen to sell games through their own websites, but many turn to the monolithic marketplace of RPG sales: DriveThruRPG. Despite some overlap with Kickstarter and Patreon, DriveThru is clearly the leader in both physical and digital RPG fulfillment.
That being said, a curious challenger to DriveThru’s platform has begun to stir up some discussion within the indie RPG scene: itch.io.