Why they say keeping a cell phone close to the head increase chanse of cancer?

Does it really matter if the phone is close to you, because the wave that a cell phone tower or a setilete emits goes out everywhere and not directly to the phone, it just happens that yuor cell phone picks up that signal, but the same signal could be picked up far away from you, Same thing if the cell phone emits waves it goes out in a circle kind like a ripple in the water and hopefully that wave would reach a tower in the close enough area, but its the same exact signal a foot and 500 feet away isn't it? So it doesn't matter if you use a cell phone or not because the waves are always around you, right?