The 2DS came out October 12 with Pokémon X & Y and only sold 30% of the 3DS family from October 12 to December 31st 2013.
The 2DS from January 1st to May 31st 2014 only sold 20% of the 3DS family, even though it was sold at $99 at all retailers long before that part of the year was over.
It has been estimated by many, that somewhere around 85% of 3DS owners ages 13 & up, use 3D on their 3DS/3DS XL.
Where the hell did you get all this info?
At least from what I see on the internet and from the people I know, I'm one of very few who actually use 3D.
The 2DS only sold 2 million out of the 3DS family 7 million from October 12 2013 to May 31st 2014.