Interesting. We have a 12' x 80" 7K trailer, and 18' and 20' 7K car hauler trailers (plus a horse trailer and a stock trailer), and 2 crew cab long bed 1 ton diesel pickups. The trailers are great for getting hay in the summer and moving the tractors when needed (rarely), but we use the trucks for pretty much everything else. The 12' trailer has been really handy pulled behind the tractor cleaning up all the branch that came down during the snow & ice storm last month, but normally it sits most of the year.
Two of the reasons we don't use the trailers are due to the ground is soft over half the year, and trying to get a trailer positioned wherever tears the ground up a lot more that just using the trucks, and the 12' trailer can be a pain to position because of how short is it (compared to our rigs). Plus, it is easier to just use the trucks!
So aside from hauling hay into the barns in the summer, I would say we could do without the flatbed trailers pretty easily. If you had a short bed truck or the even shorter ones on some half tons, and your ground didn't turn to mud the second time you drove on it, I could see where a little trailer would be handy, especially if you had a short wheelbase tow rig to maneuver with.
Ed