We do too. They’re not simply decorative. And my wife has cross-stiched a custom stocking for each kid so they’re pretty big (the sons’ girlfriends get one once they’ve been a couple long enough that it seems they’ll stick - only had one get a premature stocking 
).
It goes back to when they were little. They were up at dawn so they could take their stockings down and unwrap things in them while we staggered around looking for coffee or cocoa to wake up (Santa usually stayed up 'til 1am so they were seriously asleep before loading up the tree…early morning wake ups were killer).