Every job ad I've put up since starting my company has had over 100 candidates. 80 of whom are wholly unsuitable and do not send any cover letter. Another 10 don't bother with the cover letter but may have been suitable. All these are instant rejects with no feedback.

The 10 I phone interview I will at least give feedback to, likewise the 3 who we eventually interview.

Given so many no hopers though just clicking apply or sending a generic CV, I'm not surprised the vast majority get no feedback.