"And ties - what purpose do they serve other than social signals?"

Here is an answer: <exaggerate>I am the slave of my company, that's why I wear an expensive, totally useless thing around my neck, that lets me sweat in summer and breathe hard all year round. My company asks that and I do what they say, because I always do what everybody does. And I rather shit my pants than to hold the minority opinion :o)))).</exaggerate>

Well, you are right, its also a social signal.

Depends on the quality. A $300 silk tie sends a different signal to a $2 tie from a supermarket.

It's still a very expensive, very soft, noose around your neck.

You'll notice that ties are (thankfully) finally starting to die out. I've just spent a few weeks in back-to-back meetings with very senior execs, and maybe 1 our of 5 people bothered with a tie.

Industry reports show that the neckwear business is hemorrhaging after peaking in 1995. Good riddance.

Useful for blowing your nose on?

I suppose if you wear one around your head it signals something, socially.