Everybody has one pose. One pose that if you ask them how long they've been doing it, they'll answer that it feels like forever, but yet they get no further than where they began.
You can blame tight muscles, stuff joints, general lack of flexability, there can be lots of reasons. Totally legit ones, its just that that pose seems to never go as desired.
For me, that pose is Baddha Konasana, aka Cobbler's pose, aka Butterfly. My feet connect, they get within 12 inches from my body, I lean forward about half an inch, and done. I watch others lean forward with no problem, some even with their face to the ground. Nope. Not gonna happen with these hips of mine.
They really aren't even tight in other poses, just this one. It's as if you could take a sledgehammer to these knees and they wouldnt budge an inch closer to the ground. Same with my chest.
But I'll keep working on it....