That's because they don't need to talk to you to obtain your info. It's a computer robo-dialing to collect viable phone numbers, and potentially more. It's never a good idea to answer unknown calls, no matter how irritating they might be. ;)
I have had this number call me about 3 times now. All say out of Shelton, WA. I reject it every time. I never answer numbers I don't recognize. If it's that important they will leave a message.