I think I understand the idea of blocked phone numbers. People don’t want the person on the other end of the phone to be able to call them back. Maybe they are calling from the back line of a doctor’s office. Maybe it’s a personal cell phone. I’m really not sure who they are.
If you call my personal cell phone from a blocked number, be prepared to be ignored. If your phone does not at least have a number I can identify, I surely am not going to pick up the call or call you back. I may be an old fart, but I want to be able to identify the person I am talking to. I don’t think this is covered in the etiquette books, but it probably should be.