Mainly because Virtual Volumes are considered to be the VAAI evolution VMware decided to move the VAAI feature into the vSphere Standard edition as well.
That should make many Standard users happy, as long as their storage is VAAI supported. Especially for storage systems having asynchronous active/active VAAI makes life easier as the optimized path is chosen automatically.
Cormac Hogan also published an article about.
Photo courtesy of VMware Inc.