Requiring a full URL will be more of security thing I would guess, as some users put HA on the internet and it could have access to open doors.
Also I have tried things on sub paths and it got very complicated to know where a service was, a domain keeps things easy to setup and manage. As I run internet facing services for my day job, I have to look at both security and easy of maintenance when setting things up.
I would say that if you need a path over domain, its a skill issue and you need to find a better way of working.