Didn't used to, now I wear one every time. Usually it is one of my colored ones (1 gold, 1 silver, 1 red, 2 blue), but occasionally I will don a simple white one. But a suit really doesn't look complete anymore without it. And being a man with more padding I also like how a PS draws eyes up, away from my rotund.
I don't normaly wear a jacket to work, so most of my dressing with a jacket is for social occasions. Since reading many posts here, I have come to view wearing a pocket square as de rigueur.
So yes, always a pocket square, even if it is just a thin strip of white, but often it has some colour and is folded to a pattern. I am cautious with colour as my colour coordination skills are extremely weak.