Why Tu, Rather Than Vous, in Chrétien de Troyes'Le Chevalier de la Charrete?

Why Tu, Rather than Vous, in Chrétien de Troyes' Le Chevalier de la Charrete? In general, Chrétien de Troyes avoided mixing tu and singular vous in address to the same individual, used vous in a sustained manner, and had much less recourse to tu than vous. In Le Chevalier de la Charrete {Lancelot), however, tu occurs frequently, which allows one to examine second person pronoun selection in extended passages of direct discourse. Tu is not used to express anger; however, it is used by a prideful speaker to express scorn or contempt for his interlocutor. It is contrasted with vous, and used in complementary fashion with vous in disputes between pairs of fathers and sons as well as knights. The use of tu in the Lancelot — and of vous as a sort of contrastive correlative — is stylistically well suited to a romance which so greatly emphasizes shame and honor.