To be honest, and my opinion here hasn’t and probably won’t affect whether or not this is changed, but I used to prefer a large tab (like 5) so that things were more apparent. However, over the years, I like the tighter looking code in CMac with just 2 characters. I can fit more nests on the screen and have to scroll right much less often. And since this is something that can be changed to your own liking (either in ME or in your version control software), I would see no reason to change the default.
That’s my .02