Hi William, et al,
Yes, one reason is they are a know dieses vector species. Yet, this is not the only reason. Like so many wild animals and exotics, when they are "imprinted on" by humans and have their normal ethology altered they can become an issue...inturn they are often released to not a good ending, and/or brought to an area that makes them an "invasive species." Crossing them with a domestic (which has been done) is not for the "average breeder" and would require a wild "european rabbit" as this is the species (O. cuniculus ssp) modern breeds came from.
It has been my experience, with the proper skill sets, that they can be "tamed" yet I do not recommend it accept by a professional animal handler and for no other reason than "research or natural history education." When I have worked in zoos and natural history programs we had several "wild rabbit" species including a "Jack" that was well acclimated to being around humans, so yes, it can be achieve, yet I stress again...IT IS NOT RECOMMENDED.
Not that I condone such activity, yet if you like a "wild rabbit type" there are Beagle Hound enthusiasts that have "dutch & calico rabbits crosses" that emulate well wild hares for training these dogs. They have bred the "wild" back into them and they behave and resemble the O. cuniculus you would find in Europe, North Africa, and regrettably as an invasive Australia and other locations.
As for "meat breeds," as you have noted by now, there are many "opinions" about this. Flemish Giant, is but one of several breeds that were developed for the rabbit "meat trade," and like other meats each breed has characteristics that some like over others. I preferred Flemish crosses for size and "free range" abilities....and the list goes on from there of what can be done with bunnies...
Regards,
j