Cohabiting is same as Marriage?

Daily Mail - judge rules cohabitee is entitled to share of man's wealth. Rubbish. if people want the "legal" rights of marriage "GET MARRIED"!
It only takes 10minutes in a register office. Why all the fuss about Gay Marriage if it makes no difference? I thought when Cameron's law came in it would help all Married people. Where is the married person's tax allowance?