I am curious: Why don't they care about emails?
I have called them as well because I am livid about the way they keep ignoring we who pay all the bills and catering to the people who are bleeding us dry -- and aren't even citizens, to boot!
Because they're oftentimes generated at an anonymous whim, or are the preferred form of mass-mailing efforts. They're free, which means the sender only sacrificed the few seconds it took to type some incoherent, illegible babble about some issue, and you can't emphasize anything over email.
Meanwhile, with a phone call, you not only tie up a staffer, but the staffer gets an earful of a living, breathing person who decided an issue was important enough to take the time out of his day to call, pay long distance, wait on hold, and finally yell at someone.
Just like how a boss' reprimand has more effect when done verbally, so too does a voter complaining to a Congressthing.