Aeros are for aeros type people in machines designed and tested for it being taught by pilots that know what they are doing.
Same with the mill boys and girls.
Not for PPL's and CPL's fannying around in clapped out heaps with the blind leading the blind in the RHS.
Hmmm. Back in the '70s at least at Barton, I don't remember there being such a 'brick wall' between 'aeros type' people and anyone doing a PPL. Often, on completing the PPL, aeros was the next logical step for some (indeed with some instructors and with interested students, you'd no doubt have done a bit of extra-curricular aeros during the basic training phase!). But it was a long time ago, and maybe I've forgotten exactly how it was.