They can, but they don't have to! They are not losing any business by making us pay for the calls ourselves. Why pay for something you don't really need or can get someone else to pay for?
For people with issues with having to pay for the calls I guess the answer is to use a TA so that they are the ones making the calls.
The good news is that so much can be done online now--LOVE being able to set up dining online- so there really shouldn't be much reason to call. For my last trip I think I only called twice--once because I was using the Disney Visa promo code and had to do that on the phone and then again because he messed up my booking. I don't remember if I paid online or on the phone.