Whether to allow the occasional visitor or not really depends, IMO, on the nature of the listing, whether the host is onsite, and whether the guest asks permission and doesn't take advantage. It would seem wise to prohibit it entirely in whole house listings, particularly if it's a large place.
A friend who hosts a private suite in her home and has a lot of repeat guests has a an older couple who come about every 2 months to visit their daughter and grandkids. That visiting takes place at the daughter's home, and the grandparents like being able to retire to their own place at the end of the day.
However, they know another couple their age they like having over to play cards and have some drinks from time to time, and that's just fine with my host friend.
I had a guest who was in town to visit her grandkids, and although I only list a private room, I told her she was welcome to have the kids over if she wanted, as there is plenty of outdoor space. She didn't ask, I offered.
It isn't something anyone should offer the possibility of in their listing ad, but if a guest should happen to ask and the host is comfortable with it, there's no hard and fast "Never do this".