@Chozo @youshouldknow @ono Finally someone gets it!!!
Hashtags in Mastodon is what allows discoverability to posts. So if you wanna make your posts indexable you'll need them.
Mastodon doesn't index by words, just only by hashtags.

So if you make a post about cats, but you don't add the hashtag "cats" your post is like it wasn't post at all. No one can see it, besides yourself and your followers. Also I don't get why people all it spam, if it goes at the end. Easy to ignore.