I am not an expert in ophthalmology (but now at least I can spell it.)
The retina is an extremely thin tissue and it is not structurally attached to the back wall of our eye except at the optic nerve. It is usually held in place by the pressure of the vitreous humor, fluid inside the eye. Under certain circumstances, if fluid gets between it and the wall of the eyeball, the retina can fall away from its proper position. Because the retina is the tissue that detects light in the eye, obviously this will have a serious impact on a person's vision. A number of factors are involved, but a person's chances of developing a detached retina increase among people with severe myopia. The nearsighted eyeball is longer than normal and stretches the retina more thinly.
One possible reason you may know an increasing number of people who are suffering from detached retinas is that another risk factor is age. If you are anything like me your group of friends is, gradually and gracefully, advancing in age. This will naturally have an effect on the number of them who are probable victims of this problem. I wonder if the people you know who are suffering from detached retinas tend to be older people.
For most of the evolution of humankind, our life expectancy was less than half of what it is now in the United States, so it shouldn't come as a surprise that what might be perceived as a design defect like this would have little impact on people until the last hundred years or so. People typically didn't live long enough to get the problem.
