Alingment is leading whitespace that is expected to match the width of some non-whitespace text above, indentation is leading whitespace that is just expected to match all other indentations (* level). When indentation is scaled through editor reconfiguration, alignment should stay the same.

What I think gp is underestimating is just how much alignment there was in the old days, and how little (compared to now) indentation. From today's perspective, indentation is the norm and alignment is the rare exception. Your question is a good illustration: sounds like you never met alignment, or at least never noticed it. But back then, alignment was a very regular occurrence and the extra diligence required for getting all the tabs and blanks right to look nice on different tab widths, or the ugliness from failing to get the mix right would have been a considerable cost. Avoiding unpredictably wide tabs was a reasonable call.