But why does they write these stories like this one:

http://www.rcuniverse.com/forum/m_7464991/tm.htm
*****
The receiver pack powers your receiver and steering servo. The BEC function of your ESC steps the voltage from your main batteries down to 6V and uses this to power the receiver and steering servo. With input voltages too large (more than 12 cells) this functionality will not work properly which is why you need to use a receiver pack. Also you are more prone to radio glitches using the BEC.

Hope this helps.

Greg