Why does Berowne protest the vow of chastity in the play, Love’s Labor’s Lost?

In the play's opening scene, Berowne protests the stringency of the oath of chastity and study that he himself has sworn, arguing that the oath will be too difficult for the lords to keep. He further argues that "all delights are vain" (I.i.72), even the pleasure of scholarship and books. He protests the oath not only because it is impractical but also because it is selfish and vain.