Cable routing procedures for Sirius Starmate?

I'm in the process of installing my new Sirius Starmate 5 satellite radio in my car, and I just read in the user's guide that you're not supposed to route the power cable next to either of the antenna cables (the one going to the antenna on the roof and the one connecting to the actual car stereo). It says you're supposed to keep the power cable separate. Why is that?? I don't see how this matters and if I were to do that it would require a lot more work to install.