My guess is that it has to do with the transmission; the engine needs to start to allow the AT (or CVT) to be placed into either R or P (remember that in D3, D, or N, you're still dealing with a forward gear or neutral (which disengages the clutches)). Reverse engages a different clutch, and Park has it's own attendant issues with locking the driveline, setting the parking pawl, etc.
In theory, you're right - if you're putting the car into Park, you're not planning on going anywhere (I also alluded to this in another post; the one where the supposed Honda engineer asked us what we'd like to change about the cars; this was one of the things I mentioned). But if you shut down the HAH in N, move the gear lever to P, then restart the car, you'll hear a nasty little 'clunk', which after a couple of times with me, gave me the message "yes, it's wasteful to restart the car just to put it into Park, but if I keep defeating it, I'm liable to damage the tranny"
Exacerbating this is the fact that the Honda V6 AT hasn't been known for sterling reliability the last few years; Honda extended my warranty on the '01 coupe up to 100K, without me asking (and to this day, I believe I had a malfunctioning torque converter on that car)
Couple that with a new AT case housing, a taller gear set (more $ to replace, being non-standard to the other V6 AT), and a TC that is programmed to stay in lockup earlier / longer (helps w/ regen), and I'm treating this one with kid gloves - I've recently passed 12K on the odo, and will be changing out the fluid with fresh Honda ATF-Z1 at 15K, when my next oil change is due.