I never use Trunk Doors(or Heavy Duty Trunk Doors) on vehicles because I can’t use curtains to get privacy/ward off being seen while sleeping. Is there a particular reason we can’t use curtains on them? I’d definitely start using Trunk Doors/Heavy Duty Trunk Doors for my vehicle’s rear if I could curtain them.
IIRC, there is an opaque version of truck doors that you can use instead, that might be the reason why.
Personally I prefer opaque heavy duty hatches over any kind of doors since they give more cargo space and have higher HP, with well placed inbound mirrors and a camera system you have nearly the same view and a sturdier vehicle as well.
7 Cargo Carriers, a large number of 60L tanks, a bed, a minifridge or freezer, and one of every crafting station is enough for my cargo needs, and I dislike using cameras, and mirrors make my vehicle 2 wider.
neither inbound mirrors nor cameras make your vehicle wider.
Edit: miss read what you put, ignore what I said about cameras 
Is there any advantage to use trunk doors over hatches (heavy duty or not), apart for the cheaper material requirements? I usually replace all trunks for hatches for the extra “free” cargo space (usually the hatch is where I store the foldable vehicles 
), plus IIRC you can put window curtains on hatches.
Usually the “cheaper requirement” is not a problem as steel frames are easy to come by. Are they faster to open or traverse?