This is not trying entirely to ban porn.
One of the positives of havin the new domain is that if you try to google someone, and there is an adult star with the same name, you (hopefully) wont be greeted by images/videos/links of porn.
It also makes it easier for workplaces and public places to block content deemed inappropriate for public. Instead of having to go through a trial and error basis, they can do something like "Lock all
www.*.XXX sites" (I'm sure it takes more than that, but you get the idea)
Also, another positive note is that there is more creative freedom for the adult industry when it comes to naming sites. because of the different domains, you can have both a .com and a .xxx site with the same name, and have no conflicts whatsoever.