Atari eventually provided excellent support for 3rd party developers, but for the first few years they didn't support any kind of 3rd party development and kept

Atari eventually provided excellent support for 3rd party developers, but for the first few years they didn't support any kind of 3rd party development and kept the technical documentation under lock and key. Atari also didn't want to cannibalize their game console business, so they restricted the types of 1st party games they would develop for the system. As a result, they squandered their significant head start in the game-focused home computer market.