This is such a brilliantly good point!
Before getting my current job, I think I had applied to around 180 companies (getting about 10 callbacks -> 3 on sites -> 1 offer).
And I totally used an automated script I wrote for creating cover letters. It was basically a general template about me, listing relevant skills and interests, a blank variable for company name, and then an area where I could say why I wanted to work for XYZ.
Made that part of the process so much easier.
Interestingly, being on the other side, when I’ve reviewed candidate applications before phone screens or interviews, I always enjoyed reading cover letters.