Give us a good reason why they should be able too?
What is this, New York City all of a sudden? The burden of justification of restraining individuals' freedom to engage in consensual activities or enterprises lies with the government. Free people don't (or shouldn't) have to ask permission from the government to do consensual things.
@Quentin, same reason gay marriage is marginalized and used to be banned outright -- enough people think it's icky and like so gross and omg super offensive, and have so little respect for others' freedom that they think it's okay to restrain it to preserve their fragile, delicate little sensibilities.