Because it's fun to rev the engine while moving and/or at a stop light without having to put the car in N. It was designed so you can pull both paddles to disengage the tranny.

 

In fact it seems like that is the main purpose of the double paddle declutch. I base that on two sources. One is the Owners Manaul, which says this about that:
"Double Paddle Declutch - Use of Double Paddle Declutch on public roads could result in exhaust noise in excess of local laws."
Pretty much sounds like the expectation is that engine will be revved up, huh?

And, from the MidEngine Revolution Book:
"Those paddles have one additional function. “We wanted to make sure
this car has all the Corvette character,” says Kociba. So, when a Stingray
driver stops at a light and wants to rev the engine, pulling back and
holding both paddles instantly puts the car in neutral so “you can rev the
engine to your heart’s delight.” Release the paddles, the clutches engage,
and away you go."

Of course it also offers the rapid exit feature.

And, technically, its not really neutral - already mentioned. Its just a clutch disengagement. There are actually neutral positions for every one of the five shift forks, but the only way they are all in the neutral position is in the N position. Even in the P postion on the shift selector, shift fork 1 is positioned to engage 1rst gear, and shift fork 4 is positioned to engage reverse. So if you prefer to hit N at a stop light, just know that you are moving the forks to the neutral position. Normally, at a stop light, in D, fork 1 will be positioned to engage 1rst gear, and fork 4 will be positioned to engage 2nd gear. If you use the double paddle declutch, you are reducing the clutch pressure slightly, but the forks remain engaged. Not saying one is better - just different. But you can't do a rapid exit from N. I don't do either at a stop light.