Comment by Reelin

It does seem like an additional reason, but I'm convinced tabs were (are?) disliked primarily for historical and technological reasons. Historically the tab key worked with a tab stop; there's always friction when you switch paradigms. Technologically, accommodating a variable width non-printing character on an 80x25 character-mapped display for no particular reason must have seemed both gratuitous and wasteful when you consider the typical hardware of the time (monochrome terminals, CPUs on the order of 1-50 MHz, 1-5 MB RAM, < 1 MB ROM, etc).