Most Recruiters Withhold Their Caller ID - Lack of Thinking or Plain Stupidity?

Most recruiters call from withheld numbers which may seem like a good idea on Planet Recruiter but I (as most people) screen my calls and send them to Voicemail.

Then they leave a message in which they spell their name and phone number (usually the number is given twice).

So what IS the point in withholding their number if they give it out anyway?

-ulianov