I lose subscribers all the time. You notice it a lot more when you're under 100 subscribers, but once you're above 10,000 subscribers, you don't notice the change of one or two dropping off.
Some of them will be random bot accounts, and if you're the kind of creator that goes into comments of other people, or share groups asking for subs, that generally is the result of those "plz sub" people no longer finding any value in your content.
The importance of having a core value and messege. So many people focus on wanting to get a subscriber number, when they should be focusing on wanting to provide something worth watching.
Sub numbers don't matter. Yes, you need them for monetisation, you need them for stories, you need them for community posts.... that's YouTube's foolish decision when other places like Instagram let you do stories with 0 followers... but realistically, sub counts don't matter. Don't lose sleep over it.
Make good content. The subscribers will come if the content is good. I think I've lost several thousand over my 6 year journey, and that doesn't bother me one bit.