@HahiHa If you think about it, this isn't the most ridiculous event that exists. Either way, it's a thing to make celebrations out of small things now. Best example: The creation of couples celebrating "monthseries".
I've never done yoga myself, but my parents love it because it helps them relax and soothes their achy achy muscles or whatever, so I suppose yoga is pretty helpful. As for needing its own special day, why not? Everything gets its own special day.