Abandoned on the highway

Why do I see plastic bags tied to cars when they’re abandoned on the highway? There’s always a bag or a t-shirt tied to the mirror. What’s that mean? Does it say “Come tow me away” or “Don’t tow me away”?

This may be your answer:

“Raise your hood and tie something white to the radio antenna or hang it out the window so police officers or tow truck operators will know you need help.”

(Found here.)

Really? That’s it? That can’t be all. You’d assume cops would remove the flag once the incident was concluded. Otherwise, every other Joe would stop for that car (assuming you live in Niceville).