I can think of a few good reasons but this article really has all the info you'll ever need. I was surprised when I read it !
Why Massage Feels So Good | Canyon Ranch
www.canyonranch.com/your-health/.../why-massage-feels-so-good
Why do massages feel so good?
Frees up the muscles.
In one of my marathons I spent all my cookies out on the road and actually fell over the finish line. (The time keeper caught me before I hit the deck.) So I hobbled over to the massage tent and had a massage. It was so good that I then walked more than 3 km to the railway station to get the train home. (No, I wasn't showing off. Walking is good for your legs after you've just run 42 km.)