Long wave, because of the long wavelength, needs impractically large antennas to broadcast with any reasonable efficiency. The tallest ever man-made structure before the Burj Khalifa was a longwave transmitter: Warsaw radio mast. Its ground wave range is also relatively long compared to medium wave, which means that the transmissions will reach out over a much wider area (1000 km is not unusual). That may sound like an advantage, but at such low frequencies, bandwidth is at a premium, so the longwave band has to be rather small (it's just over 100 kHz wide in Europe). Combine those two effects, and and what happens is that a single medium-powered transmitter will swamp a very large area, making that frequency unusable to anyone else, and taking away almost 10% of the available frequency space within that wide area. So the longwave band is good purely from a transmission effectiveness point of view (if you ignore lightning interference) but it doesn't work too well on a economical/commercial level. This is one of the reasons the FM band was moved from 50 MHz to its modern place after WW2: the higher frequencies are much more strongly localised to one area, so there is room for a lot more stations in a given space and stations can cater more easily to smaller, local audiences, which keeps costs down and attracts more people. A longwave transmitter for a single large city is silly, but for VHF it works.