The spaces vs. tabs or 2-space-indent convention was nothing new, but the why behind them was.
So why only 2-spaces? It’s roughly the minimum indent that we can make sense of; 1 and the indents blur, any more and we waste precious coding space.
And what about the whole tabs thing? Well, not all tabs are created equal. Text editors and file viewers often display tabs differently — some as 2 spaces, some as 8 — so keeping everything sane is a nightmare. Spaces are simple, everyone understands them and things stay civil.