I may be atypical because I started a company and unfortunately used my personal cell is several places which got into sales databases. And made a political donation.
For me, it got so bad (multiple calls per day) I've stopped answering anything that isn't in my contacts already.
I think it's mainly a millennial and gen z thing-- older generations still answer all calls, at least those that aren't into tech. I think it's just easier to realize that anyone not in your contacts will either leave a voicemail or text you if it's that important.
I'm mid Gen X, and I can't imagine wasting my time answering all calls. I have my phone set to silence any unknown numbers. I'm not going to answer any call that isn't in my contact list. Voicemail a coherent message and I'll call you back and add you to my contacts.
We ignore it too. But I can tell the ones who do answer. They get extremely irate if you do not pick up when they call. As if it is their personal line to you and you should drop everything for them. I dump them into voicemail too.
For me, it got so bad (multiple calls per day) I've stopped answering anything that isn't in my contacts already.