Funny story. When I was going the coop workshops in uni they invited in some people from microsoft to talk about what they look for in a cover letter and they straight up said they don't read them.
I believe people in the hiring process are looking to work efficiently and a cover letter is just more stuff to read. They want to just read your resume because that's what will get passed around and what matters. Anything in your cover letter is mostly things they want to know in the interview.