That's because most of these people spoof their numbers and just use random numbers. Sometimes they'll even use legit business numbers. I had a number call me one time and when I called the number back, it was a business owner explaining to me that he has been getting calls all day and hasn't called one person.
Couldn't tell if a recording or human....calling about "This is your final warning to renew warranty on car" ......Which I have never had....I started laughing and they hung up. Registered in Dingmans Ferry, PA now blocked in my phone. I suggest you do the same.