That's stupid - you don't know what you're talking about. Treadmill running is like running in place - you just lift your feet up as the surface moves below you. With outdoor running you're pushing off the ground with each step. And when you encounter hills or inclines, you have to increase your intensity, pump the legs more & focus on form in order to maintain your set pace.
I don't why I'm explaining this to you - if you're a "real runner" you should know better.
The difference I get from running outdoors vs indoors on a treadmill is like night & day. Running into different elements of heat, cold, wind, rain, etc, is also rewarding as these could be some of the conditions you could find yourself racing in.
Man was made to run outdoors - not on a treadmill (wow...who would have thought).
Treadmill running has it's place for the non-competitive, recreational, fitness-type runners who want a controlled environment with the just right temp & no wind, rain, snow, etc & no rugged terrain. Lol.