Why is there a means to prove a woman's virginity (the hymen), while there isn't one for a man?

Allah possesses profound wisdom in all that He creates. The presence or absence of virginity does not indicate a woman's chastity. A believing woman may lose it due to an accident or similar cause, while a corrupt woman may retain it. The true punishment for the disobedient is in the Hereafter, and the true reward for the obedient is the bliss of Paradise.