I think xsace's point was that letting callers know they may be recorded makes them less likely to be abusive towards the call center worker and/or less likely

I think xsace's point was that letting callers know they may be recorded makes them less likely to be abusive towards the call center worker and/or less likely to make false representations of what was said to them. Of course, state (and federal?) laws make the disclosure mandatory, so it's hard to know if there's any motivation beyond that.