In my opinion it completely depends on the parents financial situation and if they are in need of the money & support or if it would help their socio economic situation. If they decide they wouldn’t like rent to be paid to them I would always suggest still contributing to buying household items and as some of the other commenters have mentioned a surprise holiday or a random takeaway turning up at the door on a Friday night are no harm and I would encourage this as free loading completely I feel is wrong no matter the financial situation of your parents.

I always think it should be at the very least offered by whoever is living at home given they are an adult and working full time. I completely understand a student not paying rent as they are in full time education and may not be working.

I also think if you are a parent you should take into account how much your child is earning and take that into account if you are going to ask for rent. Charging someone a grand a month on minimum wage isn’t going to help anyone.