I can give a real practical reason from experience - I was writing a script that needed to pull data from the database. I noticed I was doing something stupid i

I can give a real practical reason from experience - I was writing a script that needed to pull data from the database. I noticed I was doing something stupid in the SQL query, so I wanted to kill it and rerun it with the change. I kill'd the script running it, and then kill -9'd it when that didn't work. Two weeks later someone asked about my query that was still running on the database. And now I'm the one who warns people not to kill -9 scripts without understanding why it's stuck and how to clean it up properly.