I can't say for YouTube, but as a marketer, I can give you some insight into the idea from a business/brand point of view
Stickers are a nice short term gift for brand advocates. If you have enough brand advocates wearing stickers, more people may see your brand and talk about it, but this only works if you have a huge following, or your followers are all in similar, very niche circles that you want to be seen within.
It's not good however for growing direct response (revenue, subs etc) as it's not cost effective. But it can be a great way to delight your current following and make them even more of an advocate, which can only be a good thing. If it's cost effective and you're not expecting anything but that, then go for it. If you think it can grow your revenue or boost subs, probably not...