in reply to You've just spilled something on your tie at lunch... Do you:

When I originally started the job I'm in now, we had to wear shirt and tie. That stopped several years ago now, which is nice.

The place I thought a tie was most unnecessary was when I was teaching a chemistry laboratory course to some customers. We wore ties under our lab coats (and concerned me that I was going to spill nitric or hydrochloric acid on my tie, not just some innocuous food items).

Now I mostly wear ties for concerts. I have a nice tuba tie (go figure).

Plus, this is an opportunity to show people you know how to tie more than an overhand knot. :)