YouTube engagements are delivered by means of exchange. Sometimes other YouTube creators like you will Subscribe/Like/Comment/etc on your video in return for a few engagements on their videos from non-paying users in the network and sometimes it’s just accounts run by computers. They will all have profile pictures channels and videos of their own!
Occasionally YouTube will delete accounts that users mark as spam. This causes subscriber/like counts to drop all across YouTube. Sometimes it impacts our customers, sometimes it doesn’t. If you experience drops within 60 days of purchasing from us, we’ll happily refill your subscribers/likes in accordance with our free refill policy.