Why Does Discovery Vitality Only Value Going To Gym?

Why does Discovery Vitality only value going to gym? I don't think the gym is the optimal environment if you are particularly aiming at cardio exercises, especially if you live in South Africa where the scenes are much better than the machines.  I am not a runner, walking at pace for an hour (about 6.5 KM) is a form of exercise I enjoy and am willing to commit to.

Discovery Vitality recognises and rewards going to gym by arranging a discount at the gym, yet I don't get a gym membership discount for all the work I do outdoors.  I still like the gym for weights training and strength exercises,  but I don't do that as often as I will walk or cycle outdoors? With all the gadgets that are out there, my activity can be validated.

Seeing this little bit of research made me wonder even more. After all,  Vitality is about promoting a healthy lifestyle,  it's not a loyalty programme for me.

"Exercising in a natural environment that includes blue or green (like the park or by the ocean) can improve mood and boost self-esteem, according to a 2010 study published in the journal Environmental Science & Technology. What's more, it only takes five minutes of "green exercise" to reap the mental health benefits!"

http://www.shape.com/fitness/cardio/7-ways-make-running-more-fun/slide/3