These things cost money.
If sellers thought they might benefit from promoting their wares, an appearance might get some stock on show, and to try on. At best 30 people (who am I kidding, 10-15) might attend, which isn't enough potential for a seller. I had previously made tentative enquiries some years ago about getting some 'sale or return' stock sent, but all three of the vendors I had in mind back then, no longer trade. (Direct Chinese imports via Ebay put them all out of business.)
A model who specialises in wearing high high heels, would cost circa £200 a visit, even if little more than expenses were paid.
A venue would be needed. To have dedicated space, would need a flat payment or a guarantee of sales. ("You can have the back room to yourselves free, as long as we take over £150 in sales.") Or some private space for 3 hours, £100.
In my mind, the very minimum budget would be £300, and even that figure might prove to be wildly optimistic. Shared amongst 10-15 people? Never going to happen. Even a secluded space, with heel owners bringing their own shoes to show and be tried (on carpet) might cost £10 per person, and that's without refreshments needed like teas/coffees/other.
There's also that most men into wearing heels, don't actually want to socialise together. It's a fact. Look at the historic attempts over at HHp. We've had some 'meets' from here in the past, but there's never been more than 5 of us, if I remember correctly.
There are of course 'fetish' meets/fairs (or used to be) in London once a month.... Not sure even they have survived.