We did not find out for various reasons. I think you will find though what is a valid reason for one person is not a valid reason for another. Here are some of the arguments given to me when I told people I was not finding out and my reason why they did not apply to me:

You need to know so you can buy things!
We are planning on a number of children, so I wanted all newborn purchases to be gender neutral.

How are you going to decorate the nursery?
We are not having one due to renovating and having bubs in our room. Plus we would prefer to decorate with things that the baby likes, rather than our taste.

It will help you bond
I think this is very personal and can only be decided by the parents, for me finding out the sex was not going to change things.

For me I loved guessing (I was right) Also to me finding out the sex was putting an identity on my baby that may not be right, I really wanted my baby tell me who they were.

I could go on, but ultimately do what ever suits your family. Whatever you choose to do someone will disagree and sometimes in not a very nice way.