This isn’t really that nasty necessarily, it’s just really good at one specific thing–clearing light infantry out of big areas of really rough terrain. Like an elaborate trench system for example.
Otherwise you have to send guys with guns to do it the old fashioned way, who themselves suffer casualties.
The reason we don’t like them is a portion of the submunitions will not detonate, but remain live. These will cause innocent civilian casualties in the area for decades to come, if not cleaned up with extreme care. It’s not too different from landmines that get left behind. Kid goes wandering off years from now, loses a leg.