Track drops are designed to offer one hand position, i.e. in the drops.

Road drops are designed to offer 3-4 different hand positions.

Do you want to spend all the time you're riding in one position?

BTW, they're called "drop bars" or "drops" for short, but at least to me "drop downs" sounds weird (makes me think of a genetic disease caused by riding with too much saddle to bar drop).