As mentioned, it is more that the stamp collection just hasn't been updated with non-event stamps in a while. From the looks of the site news the last non-event stamp update was late 2020. Site staff had been making pride themed pets for years at that point, but they were just made more as vague references to it and we didn't start releasing pets/items explicitly for pride till 2021, so I'd expect the only reason there aren't pride stamps is we weren't 'officially' making pride stuff till after the latest stamp update.
I would also like to stress that the majority of site staff are LGBT+ themselves and have absolutely no reason to not want to include such stamps. You correctly identify that a large portion of the site playerbase is LGBT+, and site staff are selected from the playerbase so naturally the staff are of similar makeup as the playerbase (if not an even moreso since any portion of the site who are anti-LGBT+ aren't especially likely to apply for staff, much less be chosen), I just really dislike what is implied by just referring to staff as 'allies' as if many are not also a part of these groups (and thats speaking for myself as well, I've been either GH or GM on this site for 10 years now, I've made pride pets myself)
And I just would also like to add that the pets released for Pride /are/ intended as explicit references, this year in June pets were released for Pride separate from the regular monthly releases (before now Pride pets were mixed in with the June monthly releases) so there is also a
Pride section in the archives for those pets. There were also flag releases in
2021 and
2022 which list the specific identities and orientations for the flags specifically so that users can display them on pets or in their signature. I think this makes it pretty clear where the site stands on this tbh.
Just so this doesn't get misinterpreted, I want to make it clear that I would very much like to see some pride stamps released, I don't think there is any problem with asking for that to happen. I also don't mean to imply that releasing other pride stuff is some kind of excuse for not releasing stamps, I bring the other releases up cause I want to make in clear that staff have been and continue to be invested in releasing things for Pride. I do think though that this thread might be better suited as being a suggestion for a stamp update as a whole, which would include Pride stamps among others. There are things missing from the stamp collection which are also worth including (I don't think there are any stamps for Disability Pride yet for example, even though we've gotten pets and items for it), I think the stamp collection is just simply in need of a major update overall.