I had never owned a flatbed and never had any real need or desire to own one until late '07 when I was preparing to order a new '08 Ram. I wanted the advantages of the Ram cab and chassis which, of course, is delivered without a bed of any kind.
The flatbed was a compromise I chose to accept and have grown to like the flatbed for a number of reasons. It is not pretty, for sure, but it is practical.
Just several advantages of a flatbed that come immediately to mind:
Easy to hook up and unhook a fifth wheel or gooseneck trailer. No bed sides to reach over.
No tailgate to remove or worry about smashing when towing the trailers mentioned.
Large flat cargo area for transporting large and heavy objects.
Large and heavy objects can easily be lifted and set on the flatbed with a forklift or the bucket loader of a tractor.
Four large storage compartments with lockable doors under the flatbed --- two in front of the wheels, two behind.
Easy to install winter snowchains if needed.
Less concerns about scratching or denting the bed.
Here's a link to one of the popular bed manufacturing companies:
Truck Beds, Accessories, Become a CM Truck Bed Dealer! Remolques para Caballo, Ganado, Cajas cerradas, Plataforma cama alta y cama baja, equipos especiales, refacciones,
Study their website and notice features like dove tail (sloped) rear, notched rear corners, built-in gooseneck hitch pocket and ball, gooseneck trough for easy backing under the gooseneck, headache rack, LED lighting option, toolboxes built in or added on, etc.
I own a CM and am very pleased with it. IIRC, mine is the SS model. I think it was about $1800 installed. Total price with four storage boxes put the total price to close to $3k IIRC. My CM bed is almost three years old, has been used a lot, and is holding up very well. I would buy another one.
There are lots of flatbed and towbed manufacturers all over the country. They all are built and look pretty similar. One thing I have noticed that differs with some other brands is the way the headache rack conforms to the shape of the truck cab. Some are pretty ugly IMO with sharp squared off corners. The basic CM bed like mine looks pretty good. The headache rack fits the cab back.