The problem is that broadcasts are exactly that: broadcasting. They transmit in all directions. While you have bandwidth constraints in wires, they're all localised to the wire. Even parabolic dishes (which make getting a signal a huge PITA) still aren't as localised as cables. Wired connections get a bad rap, but they're actually a much more preferable (and scalable) medium for transmission than radio waves.

Not to mention that "bidirectional beams" is another way of saying "noise".