Film pornography quickly becomes boring because it focuses primarily on one very superficial aspect of sex: the physical act.There are times when merely engaging in "the physical act" has its place, but the majority of humans eventually seek something a little more meaningful and profound from their partners.
It's very difficult for a lot of reasons for film to accurately depict a loving couple making love. When this is done successfully, what the audience sees is not pornography, but an instance of one of the most tender and life-affirming behaviors in which two people can be engaged.
It's easier and less subject to censorship to show a murder from six different angles and in slow motion so as not to miss a single bloody detail, but God forbid trying to show a caring couple giving each other pleasure....
No contest which picture kids are allowed to see more often.