Probably also makes for a more predictable experience; you don’t want to show off your shiny new engine and have a subset of people getting a poor experience because of their varied hardware (which I guess is also a marketing reason)
Epic is worth almost $30b. They make the largest 3d engine and own Fortnite, a franchise worth billions on its own. They have their own game marketplace. Their legal team is squaring against Apple. They've got more resources than a tiny indy shop these days.