[boost] [optional] memory use for optional refs and ptrs

Hello, I'm looking into boost::optional<> as a replacement for some of my code which has to deal with optional values. However, it seems that cases which are usually space-efficient optionals (e.g., ptrs in the form of a null-ptr) do not have template specializations. In other words, boost optional templates store a bool and the memory footprint of its template parameter, regardless of type. I.e., optional references and pointers take their space plus the space of an extra bool. Is there a reason for this? Thanks, Rutger