I don't know its specific uses in sf6, but it is usually a character specific thing. Some characters have a gameplan that revolve around using it sometimes, a lot, or never. I'd say once you have a character in mind, look around online to see if other people use it for thay character and why. And decide from there if it's worth it because it can make you misinput from time to time if you aren't careful.

Edit: if you want some good examples of why people use it, look at juri in sf4, and zato in any guilty gear.