There is a difference between having house rules and implementing unreasonable expectations.
Living with family as a young adult can prove to be difficult. It is a time when you are hopefully taking your first steps towards independence and providing for yourself, but you may still feel constrained by living under the influence of your parents. A good balance between freedom and structure is something that many moms and dads with kids this age are not very good at achieving. Some coddle their kids far more than they should, and others seem to expect them to take on all kinds of overwhelming responsibilities the minute they turn 18.
It can be a lot to deal with alongside all the other challenges of being in this age range, but in this economy especially, a lot of people feel like they have no choice but to stay with family. It is a necessary stepping stone before they can find their own home.
It isn't unreasonable for parents to expect their adult children to help around the house if they live with them; in fact, many would argue that it should be a mandatory condition of this arrangement. However, they have to acknowledge that their contribution should be balanced with everything else that they have going on in their lives. There are only so many chores a person can do every day if they also have to work a full-time job, as well as find the time to do things outside of that.