Dedicated Apps are dedicated to my device, mobile web pages aren't.
Mobile Safari doesn't automatically zoom because Apple were to rushed to take that feature out, it auto zooms because Apple went out of their way to add it. Same with the phone/tablet/whatever. You don't know why I'm zooming either, maybe I'm in a moving vehicle or using it at night in low brightness and can't see well, or without glasses or when tired or while holding something else and viewing at a distance or anything.
As a principle, content is there to be used not to be aesthetically perfect, and content overriding the local display device is giving control to someone without the context to make useful decisions.
I know apps don't zoom - haven't we been complaining about resolution independence in desktops and implementing magnifiers and ctrl-scroll and other clunky workarounds because of this for many many years?