I very rarely use my IR at all whilst I'm teaching PPL. I've used it twice in anger whilst teaching because the weather caught me out and VFR was not an option to get back.
Occasionally if I can't get a good horizon I'll try and pop out on top for training purposes such as S&L, turning etc where I need a good horizon to conduct a decent lesson.
Right from the outset of their training they need to start learning the local area, so that by the time solos are looming, they are happy with where features are in relation to each other in order to rejoin successfully.
IMHO Flying in 5k and accepting vectors is great practice for the rating but not beneficial to the student.
Even the circuit can be disorientating in that low viz.