You've chosen to have a unique setup, which is fine, but your use case represents some absolutely miniscule fraction of users. On top of that, it's not even that websites are unusable, just that they're not ideal.
When you decide to do weird/special/unique stuff, don't expect the world to adapt to you. You can rotate your monitor back or live with it. The idea that companies should spend engineering/QA/PM resources to deal with this is... vain.