Yes. They may not want people to know they are considering leaving their current job. And they may not keep their job if people find out they aren't fully committed.
It’s immoral behavior on the employers part to not ask for permission. IMHO it shows how they will be to work for if you take a job.
I don't get why people downvoted you. It is definitely expected that potential employers ask permission. People may apply while having a current job, and not wanting their boss to find out.
Wow, I didn't realize my expectation was so different. I've always assumed people wouldn't contact my current employer, but why not my previous employers? You're right that it's better to ask permission, then you gain more information about the relationship too. Hm.. good food for thought.
Not everything on linkedin is up-to-date or correct. Then there's the issue of some people personally knowing others but the information not being on linkedin. It's pretty easy to accidentally cold call someone for references who will talk to the candidates current employer, and this may even be the reason the candidate left them off of the reference list in the first place.