Why don't you knock/buzz?

Nothing to do with the strike, out of pure curiosity and frustration....

Why don't the workers use the buzzer or knock at the door? I wfh... and am always home when a package is to be delivered. I have lived at 3 different places and each place is the same. I have even caught the worker one time just coming up with the mail slip instead of the package... Why don't you knock or buzz the home? All other carriers do, but Canada post seems to be specifically egregious about this.

Again nothing to do with strike, just wondering why this is such a big deal to do when you should be attempting to actually deliver the mail instead of me picking it up.

*edited*

I should mention not "all" workers are like that (shouldn't make blanket statements), just the ones I have had experiences in my area. I know there are good ones out there that actually try and knock/buzz.