They also add a lot more weight and eat up valuable space from the huge wheel wells. Which is a deal killer for a lot of folks so I wouldn't pivot to far especially when 90% of the trailers on your lot are single axel.
There are compromises, but once you get to a size trailer larger than a pop-up style Jeep trailer, which is best with a single axle, and move on to a larger unit with more interior room and one better for traveling, the added weight of tandem axles is a small percentage of the overall weight. And the small amount of lost interior room, under the kitchen counter, or under the dinette seat, is a worthwhile compromise for the added ability and ease of use that a tandem gives. To me, the added stability while towing and the added ability in rough terrain for that size trailer is a a no-brainer. And any proper tow vehicle should have more than enough extra capacity to deal with a couple hundred extra pounds. I tend to put on a lot of highway miles, then drag the trailer through the roughest terrain I can manage. On the way, I stop in the desert or at truck stops, or rest areas for the night. This requires a trailer that doesn't need any setup to stop for a quick break, or for the night. A truck capable enough to deal with highway grades and back road terrain while pulling a 6,000 lb trailer. That means one rated for about 10,000 lbs. A 3/4 or 1 ton rig. I went from a Ram 3500 Cummins, which was a great highway truck, to a Tremor with the 7.3 engine, which does highway and off-road very well. I also went from an Oliver LE2, to a Black Series HQ19, to an X22, and now to a Roamer1. All tandem axle trailers, and all but the Roamer1 have been dragged as far into the back country as possible. Every one went farther in with tandem axles than they ever could have with a single axle. And once there, provided a fine little cabin in the wilderness or on the beach. Pictures to follow.
