In high school I did x-country in fall, x-country skiing in winter, and track in spring as well as running each summer. When I ran, my back leg never went past the height of my knees. My rear foot would not rise up to the height of my butt like professional runners do. I warmed up and stretched before every work out, and cooled down and stretched afterwards. When I did the butterfly stretch, my legs were almost 90 degrees while the rest of my teammates would practically be 180 degrees.
I didn't run in college (wasn't fast enough) but I was still active. I ran, played basketball, rode my bike, and did martial arts. In the martial arts club, I was easily the most inflexible person. I could barely kick anyone above the waist, much less in the head. I've tried yoga a few times but nothing really changed.
After college, I worked a desk job for 5 years. I went back to grad school for 3 years (mostly sitting down). I'm 30 now and work on my feet for 8 hours a day. I can still touch my toes, but I struggle to sit Indian style.