@muz4now there's a few reasons.
1. Being the way Fediverse is, highly social compared to others in my experience, I find less value in older posts cause a lot of them are just simple conversation.
2. I host my own instance and every post I make takes up database space. So to increase my longevity without issues, is another reason.
3. Sometimes I post a LOT. Especially when I'm having conversations with multiple people. Something I've said might get taken the wrong way at some point and blown out of proportion and deleting old posts lessens the chances of that. Cause people like to dig into other peoples profiles very weirdly sometimes.😬
Hope that makes sense.👍