I think a lot of people do stay for a week in most cases more. As proved in the amount of no vacancies signs on the seafront hotels in the summer. Problem is they are of an age where they either don't stray from the hotel or only as far as across the street. Even if they did go on the pier or to other shops they are not going to want to buy any souvenirs they've all been here about 900 times before.
Re the No Vacancies signs displayed on the hotels.
Nowadays, many hotels, large or small, do very few of their own bookings. Their bookings are all managed by the on-line firms like Booking.com and all the others, who are quite content to fill all your rooms, each and every night.................at a cost ! Thus it isn't wise to interfere with their methods, as if you double book what they have all ready booked, you are responsible for finding an alternative booking for the people concerned, under threat of a fine from the booking agency. Also you have no say as to who lands on your doorstep, they book a room and certain people arrive with far too many people to be allowed by fire regulations One local hotel found a band of people smuggling !mattresses into their lift, thus to sleep more people in one room.
The whole thing is a minefield !