Why the fuck should someone's living situation have any bearing on the amount of wages they receive?! People are paid for a job of work, not based on what their outgoings are.
All those saying "pocket money jobs", do you think employers should be asking how much rent people pay or if they have to pay for transport, before deciding on their wage?
It doesn't matter whether someone is living with their parents and spending all their wages on snakebite (if that's still a thing!) or someone uses their wages for rent and commuting costs.
Your wages are for a job of work and your outgoings/living situation is fuck all to do with it, and shouldn't even come into it.
The NMW, especially for young people, is laughable quite frankly (and it's even more abhorrent that hugely profitable companies are relying on the government to top of the wages of the people they employ).
It's extremely depressing and it's shit too that so many people are desperate for these jobs paying wages, which in some counties wouldn't even cover their travel costs (especially for short shifts and zero hour contracts).