The thing is these applicants are replying to our job ads. They know our name, address,... and their cover letter/email, most of time, covers areas of our research and how they can contribute to it (after all it is a postdoc application from someone who is already Dr. someone). It is just they arrange the title of their emails in a way that they are taught as being respectful. As simple as that. We don't think we should get offended or judge these applicants from a biased point of view
As someone who has been a hiring manager, if my name has been given out and I still get a generic greeting such as "To Whom It May Concern" or "Dear Madam" in a cover letter I consider that a negative because it's demonstrating a lack of attention to detail and most likely a generic cover letter that doesn't demonstrate why this position at this company. Likewise, one of the biggest pet peeves my literary agent friends have is when an author sends a query letter that's either to "Dear Sir" or misgenders the recipient (say "Dear Mr. Fletcher" to an agent who prefers she/her pronouns and has it on her twitter bio) because it reads as lazy.
It's not that I would reject a job seeker outright for that, nor would any intern going through a slush pile automatically put a letter that made that infraction in the reject pile BUT it would prime me to perhaps be a little more critical of their resume or pitch.