Indeed, we have that notorious anti group the US military to thank for the continued funding for plastic case ammo. They are big users of the other non-traditional cases as well, like those nickel-steel/aluminum jobs, aluminum, and so-forth. Anything that makes shooting cheaper and easier to carry more ammo is interesting to the military, and me too for that matter since I can tell the difference in a mag of aluminum case vs brass case ammo, particularly at the end of the day. I gather the air services are particularly interested. A 25% difference in ammo weight could mean some serious additional rounds into the enemy from a door-gunner's point of view or one more guy (or gal) who gets out of the LZ on a trip.
For the rest of us, I'm pretty happy with brass cased ammo as a reloader, but if they want to sell me plastic hulls for a good price so I don't have to collect, sort, clean, polish, resize, trim, ... my brass, and then have a lighter range bag for my lack of trouble... well. let's just say I'll try to keep an open mind. What irks me is all the stepped-case 9mm and small-primer 45 brass I'm finding now. Having to hand-inspect every case for those situations is part of what makes plastic cases start to seem interesting.
OTOH, out at the public land used as ranges, we already have the problem of plastic shotgun hulls and steel cases. I do wish folks would clean up their litter so as to not ruin it for the rest of us, but it's true that plastic cased ammo will make this worse.