What good reason is there for couples to have sex before marriage?

To absolutely Ensure that you will not stay together after you have sex! Studies have shown conclusively that if you have sex before marriage you have more than a 96% chance of separating.

So if you want to ensure that all you're doing is having sex and that you'll never get together on a permanent basis have sex outside of marriage.

You try on shoes before you buy them. 

Because Many People Hate sex and only Find out on the wedding Night wasting 10 of thousands of Pounds for something that will never work

always Try before you Buy 

Sex is very important in a relationship. If you marry someone you’ve never had sex with, you may be sexually incompatible. That’s not something that’s easy to fix. If one person wants it way more than the other, or you don’t both like the same things, it’s gonna be a problem. Some people wait till marriage, and find that they really don’t like sex at all. Sometimes the man will be extremely selfish and inattentive to his wife’s needs in bed. Just because you love someone doesn’t mean the sex will be good. That can really ruin a relationship.