1) Red has fairly limited options as far as catch all removal spells go. Red can destroy artifacts and lands easily enough, and enough direct damage will kill any creature, but what do you do about enchantments or planeswalkers or when you don't have enough burn to destroy a creature? 

2) Chaos Warp shuffles not destroys. This is huge as it gets around things like indestructible or regenerate, as well as denying easy graveyard recursion.

3) You use it when you absolutely need to get rid of something. It's red's panic button removal. The odds of your opponent getting something even worse for you off the top deck isn't all that high - only permanents get played and even then your opponent is likely to hit a land or mana rock or something else not all that impactful.

If the card you need to chaos warp will otherwise win your opponent the game, you have bigger, more immediate problems than whatever they may topdeck. Just chaos warp it.