Long distance running is not especially good for health or the heart. Marathon running and long distance cycling are actually quite bad for the heart. There's a ton of stuff out there now about disturbing rates of sclerosis in marathon runners.
Running 5Ks (not crazy distances) is surely a lot better than doing nothing, but I don't think there's any evidence it's better for you than other pursuits. Olympic lifters have excellent blood profiles and body composition, for example. Probably true of squash players.
Running is popular because it requires zero athletic ability and no equipment.