Even "hairdressers" hmm need qualifications.
Why put it in quotes, as if I was implying that hairdressing is not a good thing to do?
Don't salons select hairdressers based mainly on their hairdressing qualifications and experience? Would a salon really reject somebody just for not having a 5 in GCSE maths if they had 5+ years of experience in hairdressing? Why?
And a previous High Master of Winchester couldn't get a job as a supply teacher after he retired until he had taken GCSE maths.
You would need to quote the precise circumstances for this to be meaningful. It is not the case that you need (British) GCSE maths to become a qualified teacher in the UK - you can take an equivalence test see e.g.
www.educateteachertraining.co.uk/routes/
On the other hand, it is plain crazy that somebody with a PhD in Mathematics from a UK university who did not take GCSEs (due e.g. to being from abroad or being home educated) could be prevented from teaching Maths by not having GCSEs in English and Maths. (The PhD in Mathematics clearly requires knowledge and skills in Maths and communication/writing skills in English well beyond GCSE.)