perhaps people should get their heads out of the gutter and stop thinking dirty. Not all 2 adults get in must mean........ ahem you know.........

What if it was a 'medical or disability' reason that the person must be accompanied by another? Not all disabilities are visible. Rub it the wrong way and the airline will be slapped with a disability discrimination lawsuit (in North American context)

Nonetheless, one can argue two or more locked in a privacy moment may raise security related concerns too.....

Just my two cents on it....... not so clear cut.