How and why are there age-restricted 55+ housing communities?

The one my in-laws live in also has a fence around the perimeter, a gate at the front entrance, and a security guard who clears anyone who enters the community. Inside, it has all of the amenities above, plus a golf course with golf cart riding trails all over. There are several scenic lakes along the golf course that attract interesting wildlife. The HOA takes care of mowing the golf course and also the front and back lawns for every home; owners only have to worry about whatever custom landscaping they want (or they can choose not to bother) in their yards. The security gate means no one comes in unless they’re cleared and have business being there and you never have door-to-door solicitors randomly wandering around knocking on people’s doors or unruly groups of kids hanging around. The golf cart trails make good walking trails in the evenings. As a woman, it’s one of the few places I feel absolutely safe and peaceful walking around outside, day or night; I imagine that peace of mind is invaluable to retired, elderly people, since they’re generally a population more likely to be taken advantage of. Not having to do or arrange lawn care is another huge plus for an aging population. My in-laws’s clubhouse has a mini book library and a nearby warehouse with an equipment share library, so you can borrow a cane, walker, wheelchair, potty chair, wheelchair ramp, or whatever you may need. The clubhouse also has a pool, restaurant, small workout gym, large and small meeting rooms, etc. They hold weekly classes tailored to seniors, like water aerobics or chair yoga; weekly club events, like poker, bridge, and quilting; and annual events like a 4th of July barbecue with entertainment. As mentioned above, they also often have scheduled bus trips to things in the community—shopping malls, theater, ballet, museum, etc. Getting to ride to those events with a spouse or friends and not having to drive yourself is great for aging drivers, many of whom are less safe drivers or have difficulty driving at night, but don’t want to be shut-ins.