The very first time I saw my code with tabs in it on a webpage, malformatted, I never used tabs again.

As someone argued to me, if there were a proposal to introduce the tab character today as something new, people would be incredulous. "So wait, this character doesn't represent a fixed number of spaces? It represents the number of spaces required to get you to a given multiple of columns? And what that multiple is depends on the individual developer's settings on their editor??"