Social Science of picnicing

In order to understand this phenomenon, we must first dissect the whole picnic idea. To picnic, you need:
1) Food - Food is the linchpin of the picnic. Without food, it'd be a bunch of dumb folks sitting on a blanket, otherwise known as a dimwitnic.
2) Space - Sufficient space to spread out your blanket. The space typically is a grassy area, with some trees for shade, ideally with a nice view (e.g. body of water, mountains, etc). And you need space for the kids to run around and play.
3) People - Usually family and friends.

So if you're white folk, living in the 'burbs, you can "picnic" in your back yard. It's the "ethnics" living in the urban setting that need to picnic when they want to get together with family and friends. Because,
a) no room for 30 (additional) people in their tiny apartment.
b) want to get away from the nosy neighbors who'll invariably want to mooch off their food.
c) can't cook for all your friends and family in the tiny kitchen of your tiny apartment.
d) want to get away from the urban setting and pretend for a few hours that they live on an estate.

Hence, picnicking was developed out of necessity by urban dwellers who live in small spaces, aka not-whitey.

Oooh. I'm gonna hear it now!