People mention a lot how important hashtags are for discovery on mastodon/fedi, but one thing I never see mentioned is that when you follow or search for an HT, you only get results from posts that have federated to your instance (ie posts made/boosted by someone at least one person on your instance follows).

On huge instances, nbd; but on smaller ones, HTs may seem significantly less active than they really are.

If you like following HTs, boosting HTed posts makes it a more effective feature.