I think it’s mostly for the low life bulwark build. I think a lot of folks let themselves get hit a few times to drop down to like 20% life then cast bulwark and from there I believe any incoming damage is affected by your DR when injured which makes low life bulwark mega tanky since DR while injured scales so much higher than other DR stats but you have a huge barrier so it doesn’t eat into your HP.
Maybe other uses though.