There are still many that won't accept it, but people love plastic security blanket. It hasn't fully taken on off in paper, but the big surge happened in coins around 15 years ago.
I remember in 2000 when I was into coins and dealers would laugh if you wanted to slab an AG 16-D dime. Then around 2005-06 circ semi-key and key dates began to appear in plastic. Now common mid-grade classic type is in plastic. Finding original VF Barber material raw is damn near impossible. My dealer friend had a tray of raw low grade problem and original semi-key and key date coins for 20 years--that never sold. He slabbed them (without altering the price mind you) and none of them lasted a week.
Maybe someday we will see circ common 34-50 small heads in plastic in droves?
Plastic is what sells...
I can see auction houses and eBay forcing the grading issue, too. Of course, if the price of small size crap keeps going up like it is now, it might behoove everyone to start grading all their small size stuff!