There are people like me who use voice calls about half the time for work. My number is on my email signature and my emails may get passed around, which I don't mind. When I arrive to a new work site I give my number to at least one person, more commonly three or four. So if I practice what seems to be common today of not answering numbers I don't have saved, I could miss critical communication, and waste time hearing a voicemail and calling back.

I'm not saying one or the other is more correct, just that there are different situations to consider.