As a bear chaser of ill renown since the day I hatched, I guarantee you that the "competition" that exists for adonis-type guys exists for big guys as well. Fat and chubby guys ARE desired, and are NOT just a fetish.
I find a variety of large body-types irresistible, and I want to see more of them in marketing. Maybe it's just the bubble I've created for myself since the pandemic (Not maybe, it very likely is), but I was under the impression that gay guys have opened up more and more towards finding a wider range of body-types attractive.
All that said, those shops should be taught a lesson. Sex and fetish play are not exclusive to conventionally attractive bodies, and our world already deals a way-too expensive hand to those that aren't that.