[boost] thread encapsulation with private attributes

Hi, I was thinking about using boost as much as I could on a proyect. The idea of using the pthread encapsulation ocurred to me. But I found that the interface was pretty poor. I guess it is like that cause of portability. So I thought, ok... I can inherit from it and encapsulate the pthread (thats my case) functioanlity I want. But to my surprise the pthread_t variable called m_thread was declared PRIVATE... why is that?!... I mean... why wouldn't u want somedy to inherit and extend the functionality to the user's will? thanks for clarifying my doubt. Nicolas-