Anna Nystrom in yoga pants expose here curves in some hot posture. Each of these legging options give her a different look.
There is no place or time where it's inappropriate to wear yoga pants
Yoga Pants according to wikipedia is called: Flexible, tight-fitting pants designed for yoga, as well as other activities that involve a lot of movement, flexion and stretching. Some of the other activities include: martial arts, dancing, pilates, aerobics, discos, etc.
Men are visual beings and this is a visual display of detail that most guys never get to see. THAT is why men like leggings on a female.
In yoga pants your curves are clearly visible. So girls who wants to show their curve can wear it. Yoga pants make them look damn hot.