AICR made a list of "America's 50 Worst Charities"
http://www.tampabay.com/americas-worst-charities/
But they *are* a charity, however sleazy, so they aren't bound by Do Not Call laws.
As for why they don't leave a message, there's no reason for them to do so and plenty of incentive for them not to.
Every second they spend leaving a message on your answering machine or voicemail is wasted time they could spend dialing (several) other numbers. Few people respond to these pitches at all but the number who respond to a *recording* left on their answering machine is pretty much zero! Their only hope of getting money is by talking to someone in person — so leaving a message is a just an inefficient use of their time.
They don't want you to know who they are until they can talk to you. They could be worried that if you know who they are you'll block their number or simply ignore their calls.
(See http://800notes.com/forum/ta-81ff6ce50955942/why-don%27t-they-leave-a-message)
Sorry, I'm getting my bottom-feeder "charities" mixed up: It's the Children's Cancer Research Foundation that made the "50 Worst Charities" list. AICR, the American Institute for Cancer Research does, however, rate a whopping ZERO stars at Charity Navigator:
http://www.charitynavigator.org/index.cfm?bay=search.summary&orgid=3264
If you are visiting this website we suspect you are concerned about telephone calls you have received from the American Institute for Cancer Research or AICR.
We sincerely apologize if our calls have upset, offended or inconvenienced you in any way.
You may have registered with the National Do Not Call List and wonder why you have been called.
You should know that charities, nonprofit and political organizations are exempt from the National Do Not Call requirements. However, we don’t want to call you, if you don’t want to be called. It is AICR’s policy to always honor a request to not be called.
The easiest way to be removed from future telephone solicitations by AICR, is to complete our Do Not Call form at www.aicr.org/dontcallme.
Once you complete the form we will suppress your telephone number from future fundraising campaigns.
The American Institute for Cancer Research is a national cancer charity focusing on the link between diet, nutrition and cancer. In our most recent fiscal year (2012) where audited numbers are available, together, research and public education programs accounted for 65% of all expenditures, with fundraising 22% and administration at 13% of expenses.
It may take up to 72 hours to remove your information from our telephone fundraising campaigns. If you would like to speak with someone you can reach us at 1-880-843-8114 weekdays from 9am to 5pm Eastern Standard Time.
We hope this information has been helpful.
American Institute for Cancer Research
1759 R Street NW
Washington, DC 20009