Fired MSPs and Syadmins locking ex-employer/client out of their own systems?

Almost every week there will be at least one "Sysadmin left/got fired and changed all the passwords" or "Changed MSP and they won't hand over our domain" thread on here.

This is alien to me in that I simply don't understand the mentality as I would have assumed doing this kind of thing is a quick route to a lawsuit and/or jail time vs. whatever level of satisfaction it may give you.

Two questions -

• Have you been on the receiving end of this?
• Have you ever done this to an employer or client and if so what was going through your head at the time?

TL;DR why do people go all Terry Child's on their employer?

EDIT slightly intrigued by some of the MSP's posting suggesting that passwords to clients systems belong to them until they're paid which feels wrong to me.