In my experience the acquiring company will require an NDA since as a public company they would not want early acquisition discussions disclosed. I've only done one such transaction but I understand this requirement is typical.
The company to be acquired also wants to have an NDA in this case since in the event that the acquisition does not proceed you don't want your negotiating position revealed to other potential acquirers before you have chance to even negotiate with them.
The company to be acquired also wants to have an NDA in this case since in the event that the acquisition does not proceed you don't want your negotiating position revealed to other potential acquirers before you have chance to even negotiate with them.