How can you marry somebody but signed a pre-nup?

When you marry somebody you are suppose to spend the rest of your lives together. You take some serious vows "Until death do us part" "For better or WORSE" A pre-nup in my opinion is a signal of insecurity that you won't probably last and thats the TRUTH. Seriously if you are MARRYING them and you know this is the love of your life WHY do you need a pre-nup for "just in case"? I feel this way if you need to sign a contract to marry somebody it isn't genuine its a marrigae with uncertainity in it.. If you don't feel 500% sure this is it then do NOT marry them. Pre-nup=When we get divorced you cant have my sh*t and the vows "For better or worse, till death due us part." we took don't matter and insecurity...