I think there is a difference between running short bouts of Max speed sprinting versus running long periods at a lower effort. It is the difference between zone 2 and zone 4/5 running, taxing different systems (aerobic vs anaerobic).
I am not saying there is a need for speed, power, agility training as well, but I think it is achieving different things than long, slower runs.
You can easily take a 5km run and increase the effectiveness: go faster.
Fitness runners always fixate on distance. No speed, power or agility training.