It was not necessary sacrifice. The newer ones got wider, taller, and the cabinets got heavier and the tanks got bigger.
Up until the gas crunch in the 70's most folks towed their trailer with the family car. Once the body on frame car died, most people started towing with trucks and suburban. Marketing showed folks wanted more room, more capacity, and more amenities so the factory built it. Since 90% of new owners were towing with a truck weight was not so much of an issue.
Fast forward to the present and the small to medium sport ute is now the most popular vehicle on the road. So now the factory has gone back to basics in some ways. There are now smaller trailers that have lighter materials, smaller tanks and are narrower.
Supply and demand at work.
We fulltimed in a 77
Sovereign 31 foot trailer. The dry weight was 5000 LBS. The same floor plan, 82 trailer with almost the same tank capacities was 6800. Five years and 1600 lbs!