There’s a measurement issue on the beauty question as well. Height is trivial to quantify, but what is the unit of measurement of beauty?
There are definitely consistent biologically rooted norms of what is beautiful, but this is a very controversial and culturally loaded issue that would make any taxation scheme (or any other policy relying on some measured “beauty” trait) far more difficult to pull off.
Banter declares interest and leads to mutual laughs. When you laugh it’s a good excuse to touch/make contact. Contact becomes more and more common, and the “excuses” for making contact become less and less. Eventually once you’re both comfortable making contact and are close together, there’s some lull in the conversation, and you fill this lull by leaning in and kissing them. Once you’re kissing you’re able to escalate physical contact until you eventually have sex.