They tell us to do it in Canada too. But seriously, if you hiring me depends on me sending a mail to kiss your ass, fuck off, I take back my application.

No, it's not.

That being said, I've interviewed dozens, if not hundreds, of candidates, and have received thank-you notes from a handful of them. These notes are not part of the rubric used to evaluate them for the role. They also tend to come from weaker performers, so if anything, such a note is a red flag.

When I was growing up in the US in the '80s and '90s, our business classes did tell us it was proper send a thank-you letter a couple of days after an interview. This was, of course, in the days before email and workers' rights got even more abysmal in the US. Not sure if this one data point helps.

It is.