Because Tatler exists to tightly reflect (and sell to) a certain social background rather than needing to appeal to a wide audience, it’s never been “representative”. It’s like a members club in a magazine format. Circulation counts in as much as advertisers can use the magazine as a means of targeting certain sorts of high-worth people, rather than reaching tens of thousands of readers from less aspirational backgrounds.
Its circulation is just under 80,000 - compare UK Vogue at 192,242, Elle at 125,000 and Bazaar at 116,000.
Tatler also tends to swing between being fashion and celebrity-focused (like under Tina Brown) and then back to concentrating more on society, which is when the covers are an endless string of “people’s daughters”. When it’s celebrity-focused, you get more non-white faces, from Tina Turner to Talisa Soto.