If there is insufficient picture information to fit in the JPG that fits in the RAW, why do you think you will want it?
Ok, let's see mine (A570), I go into Av mode, zoom in close range to a white space on this LCD screen, and I get a spike in the live histogram.
The live histogram is divided in 5 sections by 4 lines, so each is 20%. At EV0 I get a rather
bulky sharp spike in the histogram at around 55-60% position. Then I go to EV-2, and the spike gets
thinner (thus less information, more compressed) and it sits around 17-20%. Then I go to EV+2, the spike again goes a bit thinner (larger than the -2 one) and it stops at around 90%. So the full range of my CCD is 0%-100%, and the accessible range via the EV setting is 20%-90% (or 70% of the total). So if the accessible range is 6EV, then the full range must be 8.5EV?
And if the range is half the width at +/-2EV compared to 0EV, shouldn't I try to overlap it twice to obtain the same levels resolution as that of 0EV?

Question: What practical reason would you have for +/-6EV on a general purpose photo, shot in good conditions?