Older versions of iOS had a bug where zoom levels would mess up when device orientation was changed. For a while disabling zoom was a reasonable alternative but it's not justifiable anymore
On the other points I think it's because a lot of companies are still treat their mobile UX as an afterthought, even the ones who wouldn't like to admit it. It's a lot of work to handle all the variables well and few are willing to commit the resources in the right places early enough to implement a good mobile experience without awkward technical workarounds later.
On the other points I think it's because a lot of companies are still treat their mobile UX as an afterthought, even the ones who wouldn't like to admit it. It's a lot of work to handle all the variables well and few are willing to commit the resources in the right places early enough to implement a good mobile experience without awkward technical workarounds later.