There was never any evidence to convict any of the Rs, therefore, no one was charged. Even in this forum, filled with RDIs, there are dozens of theories. "It was Patsy", "It was John", "It was Burke", "It was Burke and Patsy", "It was Burke and John"...I don't think the Ramseys were lucky. They had money and connections, which is a huge reason why they were never charged. Luck is a force that is (mostly) out of someone's control. There are a lot of people who have gotten away with murder, simply because the victim's body hasn't been found. I would consider people like that, lucky, instead of the Ramseys.
Alex Hunter was not about to charge the Ramseys and then end up looking like the fool prosecutors from the L.A. D.A.'s office from the O.J. Simpson trial. I am sure the Ramsey's lawyer's connections probably did not hurt them, but the lack of clear evidence pointing to a specific person (s) in the household made it a very difficult case to prosecute.
Even if one of the Rs did do it, it is not likely they would have been convicted. And now it appears, whatever one thinks of spacy Lacy, that there is at least a chance a male intruder committed this heinous crime.