They are kids and at that age it is pretty normal not to volunteer. They are establishing (in their minds only!) their independence from you. You, as dad, need to remind them that while they are dependent and living under your roof (even when they are over 18), contributing to the good of the household is a requirement. When this is met with resistance, you can show them what the bill is for full room and board, including cook, maid service, laundry, chaufer, landscaping, use of the entire house and property, dental, medical, incidentals, etc. Add some for profit, as that is what you'd do if an outsider came into your home looking to pay you for full care. Then show them the chores they can do to show appreciation for what they are getting for free. A little quick math will show that you are valuing their unskilled labor at several hundred dollars an hour.
They'll still argue and you'll still have to enforce the rules with consequences, but they will one day look back in appreciation when they recognize the HUGE favor....no, good parenting....that you did that prepared them so thoroughly for life on their own. Trust me on this one. Speaking from personal experience. Wish my parents (particularly mom) were even more demanding.