Sharklet_321
Quite possibly you have answered your own question.
BOH's catchment, unlike SOU, has and still is attracting mostly holidaymakers. For many years that client base was as you say, perhaps older and discerning and likely in part still is.
Bath Travel had it once sewn up at BOH, but TUI came along and the WWW, then Ryanair, and it all changed. No one is to 'blame' here.