Outside of links/top 100 courses, demand for buggies in my experience is growing. Society days and casual visitors all seem to want buggies. Like it or not, for most they are part of the day out and a good source of revenue for many courses.
Anyone can get a medical exemption these days, those who have them are far from disabled. Run of the mill members clubs such as the one I work at are investing in them out of necessity. The demand from an ageing membership, mean they are a commercial necessity and if you don't provide them, some members and lots of visitors will go elsewhere.
I too would hate to see classic courses adapted for buggy use, but in truth, the classic courses are under less commercial pressure to provide them and they are well placed to take a "walk or don't play" approach.
I actually think the massive increase in electric trolley use and everyone wheeling around a huge bag, particularly in winter is more damaging to courses.