I was just thinking about this earlier today when I opened our log.
I was faced with several hundred "ErrorException: hCaptcha configuration error: sitekey-secret-mismatch" messages.
I can see what they are - they are caused by spammers trying to post on the contact form. There are also other similar frequent messages such as the timeout on notifications which I know I can safely ignore ... to me these can be treated as warnings and not "errors" per se. Whilst its worth monitoring, I really don't want to clear all of these every time I check the log.
The problem is that "real" errors can easily be masked in the log when you have hundreds of "warning" messages, and clearing the entire log loses them forever.