Does anyone actually use hashtags to search for subjects? I believe that is the intention of them. I certainly never have, though I don't use them.
I do on very rare occasion. Often times at weddings now, the wedding will have a designated hashtag. Something like #*LastName*GuyAndGirl2018. That's a pretty cool way to see a bunch of the photos other people took at the wedding and to see if you're in any pics you might not want to be. I'll also look up hashtags during the monster truck season. A lot of footage doesn't make it to YouTube, but there's plenty on Instagram. Looking up something like #TampaMonsterJam allows me to see all kinds of footage from a big show a few thousand miles away that I'd otherwise never be able to see.
Other than those two scenarios though, I never utilize hashtags, and it drives me up the wall when people hashtag something for no reason at all other than to have one. Hashtagging something as #TampaMonsterJam is a very specific item, and is done so with the intention of sharing your footage with other fans who will specifically be seeking out your post. Hashtagging something like #ColoradoTripGoodByeForNineDaysCT, #IcantWaitToTryAllTheFood, or #ILoveTheTransitionFromSummerToFall is just internet whoring. Go fuck yourself.