That's a good question, mashallah.
A man has to cover less up but he is not allowed to look at women more than the first forgiven glance anymore than that and he is committing a sin. The men should cover up and many do.
The point of women covering themselves is for their own safety and not to attract the opposite gender. Now a woman can wear any set of clothes she wants as long as they cover themselves in a modest manner. This is by not showing their figure to strangers. This is also a Quranic injunction, so when a woman is covering herself she is in worship. This for her is an act of worship and even if the man did this he would not get the same reward as will, inshallah.
There are lots reasons to wear the Hijab most is a sign of chastity, its a sign of a righteous women who believes in God and covers herself. See the pictures of Mary (upon her peace).
Do you remember the clothing of Nuns? They cover up out of fear of God, why shouldn't others?
This goes back to the new testament where one of the strongest commands, is for a praying woman to cover her head. This is where the background comes from, I have added some interesting quotes.
Corinthians 11.6 "but every woman that prayeth or prophesieth with her head uncovered dishonoureth her head."
Jewish orthodoxy states a married Jewish Muslim cannot show her hair to anyone other than her husband. So they wear wigs and or hats.
This is the same for Muslims women
Marrying more than one woman
Generally, most Muslims are monogamous and there are no other relations outside this.
Marring more than one wife in a time can help support them in times and places where there would be no support.
After the second world war Germany legalised polygamy to solve the problem of unmarried single women.
I have heard an issue that a man married a second wife, after she fell in love with him and could not do without him. So they married and she was the second wife, this is by no means ideal but this solves the problem of adultery.
Remember that true beauty is not the skin, true beauty is whats in the heart. Beauty as they say is skin deep.