....Why would the standard over-the-air channels require a cable subscription? ABC, NBC, CBS, FOX, WB, etc...
Ok this question gets asked a lot. Here's the basic answer:
Those networks transmit those signals themselves which is in part paid for by commercials. It costs a lot of $$$ to do that. They will NOT let anyone else retransmit their content without paying for it.
See: Aereo SCOTUS decision.
You want the free transmission? Get an antenna. The moment that content goes through a pipe of some sort, it's called retransmission.