I notice IFR charts have ARTCC boundries depicted. Why? I mean why is this important for us pilots? If this is due to inform us of the proper frequency, I don't see how depicting one frequency by the boundry will help when the size of each ARTCC is huge...some larger than several States. If there are more than 1 ARTCC frequencies depicted in each given ARTCC area, I ask the first question again, why is knowing where the boundry line then important to pilots?

I'm on a roll with all the questions today. Thanks all for answering.