Its a pretty patriarchal and old fashioned idea, but I can see why some women would find it hot and fun for their man to take charge in that way, especially when it's all in good fun and there's an understanding between both partners that it's just playful teasing.
I also wonder whether part of the appeal for some women who like this kind of thing is specifically that it's their man putting them over his knee. Not necessarily because they believe men should have actual authority over women, but because they enjoy the contrast between his traditionally masculine, assertive role and their own more feminine, playful, or submissive role in that particular moment. In other words, maybe the gendered nature of it is part of what makes it exciting, even for women who otherwise believe strongly in equality and wouldn't tolerate being genuinely controlled by a partner.
At the same time, I can see why other women would find the whole thing off-putting. The idea of a grown woman being "punished" by her boyfriend or husband, even jokingly, (especially if he only spanks her and not vice versa) can seem quite demeaning and sexist.
So I'm curious: Do you find the idea of your boyfriend or husband playfully putting you over his knee appealing, embarrassing, demeaning, or just silly? And if you do enjoy it, is the fact that he's the man and you're the woman actually part of the appeal, or does the spanking go both ways?