Carol the manufacture can not give one weight for its trailers due to the different options that each trailer has which will make a big difference to the dry weight of the trialer. Besides few people tow an empty trailers without any options, so it is good to see the real world weights of the loaded trailers in general, which is what has been shown here.
Another point to consider is that a car with a 3500lb tow limit should be ok with many of the 16' but an equally as important question is what is your cars tongue weight limit? A number of cars with 3500lb tow limits also have a tongue weight limit of 200lbs or less, which can be a problem towing many of the 16's. The tongue weight on Scamps for example is different based on year and model - also how many propane
tanks, size of battery
, location of bath (up front or on the side) and ac (in the closet or on the roof),front window gravel cover etc, will also have an impact - not to mention where you stow things in general. For example I can change the tongue weight by just moving a bag of cloths from the front bunk to the back of the trailer :-) A better example would be that I use to carry bikes inside the trailer but when I changed to carrying the bikes on top of the car the tongue weight jumped up by 40lbs (and they are very light
bikes). I could have put the bikes on the very back of the trailer but that would have made the tongue weight go down - but it would have been to the point that it was no longer a safe tow. Some people suggest adding an equilizer hitch to help with the tongue weight issues but just make sure the car manufacture allows the use of equilizer hitches before you have one installed - a number of manufactures do not support the use of them. Subaru for example is one that does not.
I know it all seems a bit confusing but half the fun of getting a trailer is looking at all the different trailers and options.