I personally 100% agree with you. I always weigh the cover letter or email when I am recruiting. My observation is of lately (last few years), both the last two team leads that worked for me wouldn't read the emails/letters. And now recently I have started my own job search and not a single one of my cover letters has been read unless it went to HR first. I say this because after speaking with the hiring managers it was completely obvious they read my resume but not the cover letter sent with it. Yet the HR people had read them because they would ask me questions directly from my cover letter.

I always was trained and believe that you use the cover letter/email to highlight things your resume glosses over because none of us could describe everything we do in each tech role, or resumes would be 50 pages. So the cover letter helps to fill in the gaps, but sadly it just doesn't seem to get read now. I will say at least not consistently it doesn't get read, as I am sure there are more people like us that appreciate them.