xxx. domain names

I think it would have been a good idea to have pornographic websites use the domain 'xxx' because it would make it much more difficult for children to access them. If a child were doing a report on animal abuse they could type that phrase in on google and come across tons of websites. The problem is that many of them would be pornographic ones and the child would not know until he or she went onto the website causing them to see some inappropriate pictures. Using 'xxx' for porn sites would allow search engines to block those sites from being shown unless the person specifically asks for porn sites. I ask why wouldn't we want this? Schools have the 'edu' domain and government sites are 'gov' and commerical 'com' so what makes porn sites so special? Parents would have an easier time blocking these websites by using software to detect domain names with 'xxx' in the title and they could feel a bit better about allowing their children to do research on the web.