I think most of the OpenAI's target audience must be technical enough to know they can access websites on a smartphone and bookmark them in some way.

They probably just want to fight abuse/spam/fraud/scams that are on the App Store/Play store so that it would stop devaluing their brand. "ChatGPT charged my card $299 without permission, I am going to the press!" is a disaster waiting to happen with these scammy apps.