Actually, yoga is not "emptying the mind." There is no part of yoga that involves "emptying the mind." Pantanjali doesn't teach people to "empty the mind" in the Yoga Sutras. The Yoga Pradipika doesn't talk about "emptying the mind." Yoga is also sometimes called the "eight-fold path" because it involves eight major areas (sometimes called "limbs") of practice.
1. yama (this is universal morality--compassion, truthfulness, non-stealing, abstinence, non-hoarding)
2. niyama (these are observances--purity, contentment, self-control, self-study, and contemplation of the divine)
3. asana (body postures)
4. pranayama (breath control)
5. pratyahara (sense control--limiting or withdrawing the senses)
6. dharana (concentration and inner awareness)
7. dhyana (meditation)
8. samadhi (union with the divine)
None of these practices (even meditation) involve "emptying the mind."
In the U.S. the vast majority of yoga practitioners do so in the gym. These classes involve ASANA (physical postures) almost exclusively. Occasionally you might find a gym-yoga teacher who does a bit of breathwork (pranayama) with the class. Even in yoga studios there is often little emphasis on anything other than the physical postures. There are some studios that may offer separate classes in meditation. Studios do tend to involve a greater variety of breathwork (belly-breathing, ocean breath, breath of fire, alternate nostril breathing, etc.). Jivamukti is the only kind of yoga I know of that requires its teachers to include meditation and chanting as a part of every class. There are certain KINDS of yoga (I'm thinking of kundalini) that de-emphasize postures in favor of the more "woo-woo" aspects of yoga practice. HOWEVER, I have NEVER heard of a gym where kundalini yoga is taught. In fact, a person has to search to find kundalini yoga. It's not your typical practice.
Thus, I don't get why people get all bent out of shape (so to speak) regarding this stuff. Right now, there's lots of social media about THE PLANK CHALLENGE. When I worked with a personal trainer who knew nothing about yoga, he regularly made me do the plank. He never realized until I mentioned it to him THAT IT'S A YOGA POSTURE. I guess if someone does the plank to strengthen their abs, that's okay...but once you call it "yoga" it suddenly becomes the devil's ab-work.
There are lots of exercise classes that use unidentified yoga postures to "warm up" the class at the beginning or to "cool down" the class at the end. In fact, if you're a regular participant of group exercise, you've probably done some yoga postures unawares. Probably that cold you got, or your last flat tire, or your bad review at work were punishment for you practicing the devil-poses.
Or maybe not.
Maybe the postures are widely used because they work. Maybe it's possible to engage in these practices divorced from their origins....you know, like having a tree with lights on it in your house that you DON'T bow down and worship...or using the days of the week that all reference pagan gods. These things that were once clear references to pagan worship have been SUBSUMED by society (and the church). When I say "Wednesday" I'm not somehow compulsively drawn to worship Woden. Most Americans probably don't even KNOW the origins of Wednesday....
Just like most American yoga practitioners don't know the origins of yoga. Origially, yoga involved a guru/disciple relationship and it was men only. They aren't taught these origins and they don't even practice the eight-fold path. They show up at a class, and move around on a mat, while listening to the soothing voice of their (largely female) yoga teacher. Trust me...Pantanjali wouldn't recognize the practice if he showed up in a gym to do it.
