My first thought was that you had not checked many units out. Just doesn't seem to be an issue to a sub 2-yarder like myself. So I measured.
The tallest clearance in our bed room is right at 6-8. At the LR/BR bulkhead, the door clearance is only about 6-6. About mid-bed, the front tapers down for aerodynamics. Did not measure, since there are cabinets and stuff that made it irrelevant.
Keep in mind that this is a half-ton rated "Lite" unit, with highway clearance of 12-2. Lots of units out there are near the DOT limit of 13-6.
You would really hate our unit. The bathroom door is only 6-2!!! But I think there are plenty of units that you will like if you get out there and start shopping.