Marry your best friend (?)

We often heard about this quote: "marry your best friend." First thing I heard this quote is "AHA! very nice one!" But wait, after considering some reasons, I agree about this. Why?

1. You and your best friend must have been passing your bad and good times together

2. You and your best friend have already known your own character respectively

3. Nothing can be hidden from your best friend

4. Usually both our parents have known about us.

So, what else to be considered. Marry your best friend now!