Because you might be driving innocently through a new neighborhood to check out a house for a friend and suddenly hear a loud pop. And be covered in warm liquid. And wonder if you've been shot.
And you probably won't be shot. But the interior of your new vehicle might be splattered with fizzing, warm soda. You'll pull over and look around, shocked, dripping fizz, and be completely unsure of what the eff to do next. Eventually you'll drive home. And it'll probably be about 90 degrees out and of course you're wearing a long sleeve shirt from work, so you'll have to try and clean the mess up before you even bother changing, because OMG can't let the stains set in! So obviously you'll be sweating profusely. And miserable and cranky. Other people will probably find it hilarious - including the person who left the soda in your vehicle in the first place (who was probably your husband *ahem*).
Don't ask me how I know