Another one of my top mobility exercises (seems I'm giving all my 'secrets' away).
I like this one as many people have tight adductors aka inner thigh muscles.
Which is understandable as most daily life and activities don't involve them needing to be worked or stretched out.
If the muscles are really tight then this can contribute to low back pain in some situations.
Stretching them out and mobilising them before a workout can help improve range of motion, helping you to get more out of the leg exercises.
This is my, mostly, Personal Trainer musings and information which I hope you'll find helpful!