In my experience, if your listing shows a washer and a dryer as an amenity that is available to guests, you will attract people who are travelling around and specifically look for a place every now and again to catch-up on all their laundry! Multiple guests have cheerfully told me this. I have even come across this when I was away myself and booked into an Airbnb property that also had two other guest rooms. The other guests decided to fill up the common spaces with their damp laundry everywhere, which I really didn't enjoy.
I therefore no longer list my washing machine as available and I give details of the nearest public laundrette in my guest folder of local amenities and recommendations. I feel this is appropriate for a home-host who charges a very competitive rate - you might decide free laundry is something you want to provide for a luxury self-contained property, but then you can't really impose limits.
Occasionally, depending on circumstances, I do allow guests to do one load of washing in my machine but when they realise I don't have a tumble dryer and they would have to hang things to dry on the outdoor washing line, or in their room, most people change their mind.
