The reason, or one of them, as to why they use chemicals is because its cheaper!?!?!?

After purchasing brand new pajamas for his young daughters as a
Christmas gift, single father Jon Whelan is troubled when opening the
packaging releases a foul odor. Determined to uncover the source of this
mysterious stench and whether it poses a health risk to his daughters,
Whelan quickly discovers that manufacturers and retailers in the U.S.
have no obligation to reveal chemicals used in their products, even if
those chemicals can cause cancer, birth defects, and reproductive damage.

Full Documentary through this LINK