Ask HN: Do people really still use old browsers?

Browser developers seemt o have gone to great lengths to ensure that browsers are kept auto updated.

So as a web application developer do I really still need to care about old browsers?

My users are likely to be technically sophisticated - surely such people are no longer using out of date browsers?

I'm inclined to make no effort to support old browsers and just say "well if you're running on old browser then you're probably not my target market".