Apps are usually built so people can't skip ads. Its the only reason to have an app. Other than esoteric reasons like "we also have an app because x,y,z also have apps".
The app might make it easier for them to enforce DRM-like behaviors to prevent people from pirating creators content, but I strongly suspect people aren't doing that on iOS regardless.
For those that are not aware, on Android you can install Firefox and Ublock-Origin. Life saver!