‘You’ and ‘Thou’ in Shakespeare

Romeo and Juliet always use ''thou'' to each other, but they are the only pair of lovers in Shakespeare to do this. Why? All the women in Richard III address Richard as ''thou'', but no man ever does. Why? When characters address the dead, they use ''thou'' – except for Hamlet, who addresses Yorick as ''you''. Why? Shakespeare''s contemporaries would have known the answers to these questions becau...