That's because all the other have either floor plans that suck, not built solid and using cheap components.
Take a look at a Forest River and you will see what I mean.
2001 1500 4x4 Off Road Edition Quad Cab, 5.9 V-8
4.10 diff, Tow Package, Primus Brake Controller
EAZ-LIFT Weight Dist hitch with friction sway control
2007 Jayco Jayfeather 29A