You forgot the 30% revenue share the App Stores take.

For a lot of companies it is not a factor because they have free app complementary to their services.

Main point is that even if you could slop out some code to have a mobile app there is enough of additional burden that makes it not really worth it when you can get away with web version that is good enough and you don’t have to care about all that bs coming with publishing and maintaining a mobile app or to be specific you need to maintain exactly 2 apps.