Most households in this planet have multiple 'wires' - one for plain electrical power, one for telephone, one for internet and one for cable TV (there may be more). I had heard of PLC (power-line-communications) before, is it not possible to merge all lines into one - so that every household can be 'indexed' and 'reached' using a single line, which is principally an electrical power line. Does a power line serve better - only serving as a power line and not as a channel for communication (telephone, internet, cable TV etc)?
Why stop there? Why not get rid of all the expensive extra wires and use radio. But of course a lot of TV connections were (and are) still radio except of course cable TV. But if you got rid of the cable and went back to radio you would lose something right?
Yes, you would lose the ability to receive a multitude of TV channels and the reason is because the airwaves are cluttered with other stations competing and this creates a problem in bandwidth - you just cannot get all the different signals thru for all the customers so cable-tv was born.
It's the same with PowerLineComms - there actually is quite limited bandwidth and not enough room (currently) to get anything like the number of stations into the home (compared to cable-tv).
Power lines are usually very noisy. Any switching supply, which includes every computer, most 5V wall adapters, CFL and LED lights, and probably anything with a computer in it, introduces noise onto the wires. So not only do your devices have to deal with and filter out 120 V signals at 60 Hz, they also have to deal with all the noise from those switching supplies.