Its a mum thing. When I was a first year undergrad I used to bring washing home from Uni at the end of term and mum would grumble as she washed it.
In the second year laundry was easier and I stopped bringing it home since I always felt a bit guilty about it - then Dad took me to one side and said that my mum was feeling a bit down because I was becoming more independent and suggested that I bring home a token bag of washing so she felt needed!
Those days are gone now of course - but if I do come home for more than a couple of days, mum will insist that my sister and I give her the clothes we've worn whilst home so she can send them back with us clean and ironed*.
*If like me you don't now what I mean by "Ironed" - follow this link
http://dictionary.reference.com/search?q=Ironing