The contrary: "this person has a bunch of experience on their resume that is possibly beneficial, but their cover letter doesn't give any indication they have thought about the role they are applying for. This other applicant shows insight into the requirements of the role via their cover letter, and has highlighted key areas of their experience, giving greater detail about how it will be useful in this role."
Who are you going to pick to interview?
Perhaps this is more important for niche industries, and smaller teams. In a large team you can get good coverage of skills through sheer number of people. In a small team its the alignment of skills is more important.
When hiring (small, niche org) I carefully read all the cover letters.