There are many good reasons to say NO TO PRE-MARITAL SEX.  Some of the reasons might overlap. I'll list them here:

1) It builds patience.  This is because the both will just have to wait until marriage. The long term benefit is that it helps the couple to build respect for each other.

2) Patience == act of love.

3) Sex before marriage == impatience != love . Gals, do you want to marry an impatience man???? Think about it.

4) No sex before marriage means all the time is spend to communicate heart-to-heart. It's important to build heart-to-heart bond first, and the physical bond after getting married will be easy. 

5) It puts your relationship to the test. Do you find each other boring without getting physical with each other? If yes, then both of you better seriously re-evaluate your relationship.

6) Helps to create sense of security. The woman will know that her man will not (or 99% chance will not) sleep with other woman if he is on overseas trip for example.

7) It help the woman to filter off play-boy. This type guy will move on to other woman when he knows he can't get the women to bed after all the sweet talks and romance.

8) Zero risk of getting pregnant before marriage. (This is far better protection compared to condoms or other 'tools')

9) Able to have a good family planning. There's nothing to plan if the women is pregnant before marriage.

10) Sex AFTER getting married is 100% socially acceptable. Your grandparents, parents, siblings, friends, nephews, nieces will be 100% supporting for you!

11) Builds anticipation. Sex AFTER getting married enables a new 'discovery journey' about each others' body on the 1st day of marriage. Pre-maritial sex offers NOTHING new in this aspect.

12) It helps to protect you from getting emotionally 'blackmailed'. It's easier to put an end to a bad relationship if the relationship didn't get into a the physical stage.

13) Prevents from getting into bad situation such as getting married too early or an abortion.

14) For sex AFTER getting married, parents will be HAPPY when they hear that the wife is pregnant.

15) For sex BEFORE getting married, parents will FREAK OUT when they hear that the girl is pregnant.