DriveThru offers two important features for exclusivity (as I understand). Big publishers do not need either.
First, the publishers is paid a small amount more.
Second, you occasionally win the lottery and have your game appear on the home page again as a "Exclusively on Drive Thru" The only time I have actually seen a Better Game title there, by happenstance, was something oddball that even I forgot was put up for sale.
After the first few hours all new games get buried. If you don't have a fan base or don't get lucky, nothing you create will ever get seen. I do miss game-stores and library for the serendipity. Drive Thru is a warehouse of shattered dreams and good intentions. Mostly D&D clones.