The hashtags are working, but your videos aren't "appearing" in that populated list, because of the YT algorithm. The meta decides who's on the top of the hashtags, kinda like how Twitter puts popular tweets first in hashtag pages. In this case, I think the amount of subscribers is measured for how to be on the top x of those hashtags. Think of the algorithm as a reputation system.
So you guys definitely wanna utilize your hashtags. Tag can be very powerful and help you get alot exposure if you take the time and think about what keywords describe your content. From what I learned about SEO, the longer the keyword (3+ words are best), the more relevant your traffic will be. With that, you will begin showing up for those long search terms, plus it will increase the possibility of showing up in the sidebar for videos whos keywords are similar and match up to yours. It'd be a good idea to go back to your older videos an optimize them over time based on the understanding you gain about your audience in the analytics and for those ideas that don't always come to you the first time. If you haven't I'd recommend getting a free version of Tubebuddy or VidIQ. Anyways, hope that helps.