.....is not a good idea. Forget about the fictional tow rating, you need to be concerned with the available payload ratings. Most trucks, especially 1/2 tons will max out on payload way before coming anywhere near the tow rating.
A truck with a 12k tow rating is useless when it only has 1300lbs of payload. A fiver carries on average 20% of its weight on the pin. The pin weight counts towards payload, as does the weight of the hitch itself. Even the lightest fivers will overload a 1/2 ton truck before you add any passengers. An exception might be an F150 eco with the max tow and max payload package, but it is a rare find.
You'll see many on the road but that doesn't mean it's ok. Many are naive about all the ratings, "hey I drive a truck, I can tow anything", others just don't care. For that matter, many 3/4t trucks are overweight too.
