Knocking, ringing the doorbell, and announcing “UPS” at residential stops helps reduce theft and damages by the elements. I can’t announce UPS all day, especially on a dense residential route, without coming home sounding like I chain smoked for 90 years straight. I typically don’t touch security system doorbells, such as Ring, Nest, etc., because I refuse to talk to people through their doorbell and listen to some of the BS they spew through them.
I do knock and ring normal doorbells at each and every house though unless the customer instructed otherwise. It only takes like a second and a half tops. Only bonus babies and people that are scared to death of being ridiculed for their numbers have a problem with doing that.