Before ubiquitous mobile phones, most of those calls weren't considered emergencies.

Totally this. The reduced costs to instant communication makes some people feel entitled to your attention at any random moment. It requires a strong and active pushback.

The iOS Do Not Disturb feature allows you to set an exclusion for a chosen group of contacts, so you could allow calls from your spouse or parents while blocking everything else.

I have it scheduled to turn on every night so I'm not disturbed by spam calls at 3AM, with a few family members excluded.

same - except my DND is set for midnight until 4pm. i still check the phone at lunch or when i get to work but i otherwise wont notice it unless it actually rings.