I obviously can't answer for everyone else but my reasoning is pretty simple. The S was my first electric vehicle and at the time of ordering I decided to play it safe and get the baby S which was the S60 (which I ultimately upgraded to a 75).
Since getting the S I've found that I don't drive as much as I used to (work from home now). I used to put 30-40k miles a year on a car. The odometer on the S currently reads 10,793 over 16 months. So at this point I'd rather have a car I can keep for 8-10 years. For me, a long range 3 fits that need better than my S for a couple of reasons:
1) Range over the long run. I should never have less than ~220 miles of range on a LR 3 over the next eight years.
2) Less crap to break and if something like the screen does need to be replaced, it'll be cheaper and easier.
Additionally, It works out financially at the moment. $61k will completely cover the cost of the 3 including taxes. I looks like I should be able to get that for my S. The tax credit will be a bonus.