It's really all you need.

Probably cheaper for them than the dropouts with adjustment screws. But better than identical dropouts with no adjustment screws (IMO). As long as the drive side is all the way back all you only have to worry about the position of the non drive side to center the rim/tire between the stays and brakes. The limit on the drive side probably also assures that the derailleur cage will be in what the maker considered optimum position with the gears.

Pretty much what the others said, just more windy.