[21]

> I've never really understood how AutoCAD and Office maintained their dominance.

Joel Spolsky explained it: most users use only 20% of the app. But each user uses a DIFFERENT 20%. Thus you won't go nowhere until you are almost at feature parity, because everybody will have one little thing you didn't implement, but which is critical for them.

[vetinari]

Often it doesn't help even if you are way beyond feature parity. More often than not, it is a simple inertia, not some rational thought enumerating features.