I am a mum, I charge my son (graduated now and age 21) £100 a month.
We don't need the money, but how on earth will he ever have learn to appreciate the cost of things if he never contributes. He eats damn fine food, cooked for him, he has clothes that are washed and ironed for him (I even use fabric conditioner so they always smell lovely
). He lives in a clean, dry house that is never cold with endless hot water and toiletries available.
I don't actually spend the money he gives me, I save it towards a deposit on a house (if he ever gets one), but if I needed it, hell I would spend it to pay for what he uses! - he doesn't know I save the money BTW, I tell him I spend it on wine.
When you get your little flat and have to pay for your rent, gas, electric, council tax, water and contents insurance you will wish you were living back at home with mum because at least then you could afford a social life.
You do realise that your mum's shopping bill, gas, electricity, water would all be less if you weren't there right?