What about them? Marriage isnt limited to heterosexual couples because they all procreate, but is instead so limited because they are the only couples who procreate.
In addition, within limits, a statute generally does not fail rational basis review on the grounds of over- or under-inclusiveness; “[a] classification does not fail rational-basis review because ‘it is not made with mathematical nicety or because in practice it results in some inequity.’”...And the link between opposite-sex marriage and procreation is not defeated by the fact that the law allows opposite-sex marriage regardless of a couple’s willingness or ability to procreate. The facts that all opposite-sex couples do not have children and that single-sex couples raise children and have children with third party assistance or through adoption do not mean that limiting marriage to opposite-sex couples lacks a rational basis. Such over- or under-inclusiveness does not defeat finding a rational basis....
http://www.courts.wa.gov/newsinfo/content/pdf/759341opn.pdf
Petitioners note that the state does not impose upon heterosexual married couples a condition that they have a proved capacity or declared willingness to procreate, posing a rhetorical demand that this court must read such condition into the statute if same-sex marriages are to be prohibited. Even assuming that such a condition would be neither unrealistic nor offensive under the Griswold rationale, the classification is no more than theoretically imperfect. We are reminded, however, that "abstract symmetry" is not demanded by the Fourteenth Amendment
http://www.cas.umt.edu/phil/faculty/Walton/bakrvnel.htm
