I think the point of LFE is just noise, since as you alluded to, not only do you play an LFE signal that has a +10db gain over the other signals, the subwoofer also plays all the frequencies past a cutoff crossover that is fed to the speakers.
So, the purpose of subwoofers is to play the low FQ signals of a 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, whatever signal. The LFE signal, or the ".1", is just extra work for the subwoofers on top of what they already do--in order to achieve greater noise levels.
I guess the thinking is, better to have a more compressed input signal, then have the subwoofer take itself out adding gain to a normal signal, which might lead to distortion. Kind of like, its louder when you play the same file with two media players simultaneously (more compression), but requires less db gain from your amplifier for the same SPL playing just one source.
Edit: and for the first poster...".1" is just another way of saying LFE, or discrete low frequency channel.