Th idea is that a car hitting them is not running up a small ramp and, therefore, less likely to flip.
On the other hand, motorcyclists hate these new barriers. Clipping one of the old style barriers would make your bike slide-out from under you. This will stop your bike dead, and you'll go right over the top.
The one in the picture also has exposed legs under the barrier, these have been known to rip the limbs off of motorcyclists. A few years ago, a biker hit one of this type near Portsmouth. It ripped one of his arms off and he bled-out before an ambulance could get to him, even though the hospital was only 2 miles away and they were called immediately after the accident. That section of barrier now has metal sheet covering the posts to ground level.
