That's exactly why they're advertising them: no one uses them, and Apple apparently thinks this is because we don't know they exist.They should have advertised the gif feature instead. I'd assume that that's more widely used than stickers.
Funny thing about stickers and the new iMessages layout is that both were designed to attract younger users who mostly use Snapchat now to communicate. I asked my own kids about this recently because I was curious (personally I dislike the new layout but admittedly I'm not the target demo) and they kinda scoffed in indifference at it. My youngest likes the gifs and the drawing bit, but my oldest hit the nail on the head when she opined "why do I need it to be like Snapchat when I already have Snapchat?" All three confirmed what I already suspected: they use Snapchat to converse with friends much more than iMessage these days.