Why does a woman HAVE TO GET MARRIED ???

It's entirely upto a woman as to when she should get married....but you're right that in some cultures there's persuasion from parents...but thats only because folks are worried they would have to compromise on the groom once the girl got older

By nature, women nurture. They felt the need to get married, find security & stability, be loved by husbands, and perhaps, have children too. Men, by nature, provide. Apart from marriage, biologically men likes to mate due to laws of pro-creation of healthy beautiful babies to keep the human race going. If they do not feel the timing is right for them to settle down & provide, they simply avoid marriage. Men, by nature, likes space & freedom. If a man found someone that he can forgo part of his space & freedom, he's ready for marriage & (hopefully) be responsible & committed. If a man is not ready, there's no point in forcing him into it. Because he knows he needs to responsible & committed if he chooses to settle down.

She probably thinks that her independence will be lost.

a women cannot live alone in a society ...she need the support of a man ..

des days women r turnin out to be more independent n strong headed than men....so dont think its a must 4 dem to get married

Should get married for legal procreation to expand the generation and safety for the life fo her.

cz most women care for having babies and these stuff in some age... and they would love to have someone that share the caring feeling for her and her kids thats why they get married! and guys hate to be committed

She doesn't. There's nothing in normal civil law for countries obviously that don't arrange forced marriages that states a woman must get married. There's plenty of old women around knocking about that have never got married. Not everybody goes around shouting it from the roof tops.