I disagree too. What you call “ hobby “ subject are not just useful themelsevs, they can be part of university entry for even the most denending subjects ( I mean in terms of entry requirements ).
Say if your child applies for medicine and is taking English maths biology and chemistry at Higher. They need AAAAA at one sitting of highers. The medical school don’t care if they take MFR, social subject or Art / music as their 5th subject .
Taking a Physics won’t give them any advantage , either in terms of entry or doing the course.
So if they enjoy and are good at music ( and already have grade 5 theory and play an instrument to grade 6, as many do ) , they would be much better to do H Music ( which they will find fun and easy ) than struggle with Higher Physics or History .
Then again at 6th year. If they have an conditional offer from a Scottish uni they might ask for BB or BBB. English unis might ask for AAA or AAB.
The school might insist On 3 subjects.
The student will have to do one or both or AH chemistry and Biology. Again, their 3rd subject choice should be one they are most likely to get an A in , so again music ( for that pupil ) would be great choice .
Of they could do a crash Higher in one of their best subjects that they had to drop at 4th year. They will have a lot more choice if they did 7-8 Nat 5s rather than 6.
So that “ stand alone “ Nat 5 in geography might be handy to pick up as a Higher in 6th year if you liked it and have a good chance of an A.
It will be similar for other courses that require AAAAA at higher, such as (some) law and M Eng. Yes, they will give unconditional offers from 5th year but they are happy to accept a Higher in SOME of what you term “ hobby subjects “ as long as their essential requirements are met.
I agree that it’s essential to choose the right subjects - Higher Art or RMPS might be ok but Higher Dance or Home Ec might not.