Because of brainwashing and manipulation by big corporations which made people believe that native mobile apps are superior to web/browser based ones. The reason for this is that big companies didn't want to be sandboxed in a browser, they wanted full access of users devices, sensors and data.

It's the same reason why software developers use paid enterprise subscription services instead of open source software. They were successfully brainwashed to believe that the open source software is difficult to operate or doesn't work as well as the enterprise software. Meanwhile enterprise service companies are collecting and monetizing data from all their apps... In addition to recurring revenue.

People are suggestible and easy to manipulate, that's why. If you flash some big stacks of cash in front of their faces, they'll believe anything you tell them. You don't even need to give them any cash, just show them you have it. People follow the money like sheep to a slaughterhouse.