I don't remember ever cleaning out a washing machine filter either, though it's possible I've just forgotten. Googling the subject leads me to believe that most washers made in the last 20 years or so haven't had lint traps that you can clean out. Maybe that's why washers are now expected to last 10 years or so, while they used to last 30+ years.
I've made a few rag quilts, using 3 layers of flannel. I've washed and dried them at home with no problems, but I did have to clean out the inside of the washing machine and the dryer lint trap.