I sure would not want to deal with all the liquid when I got a puncture. I have had punctures in rear tires, one was more of an L shape cut. Rear tire/wheel assembly is heavy enough to handle filled with just air. I took it to a tire shop that was able to patch it from the inside then I went back to my field to put it back on.
Liquid filled tires ride a bit rougher as only the remaining air portion is able to compress.
The extra weight on the rear is always there whether you want it or not. And there are times with compact tractors you might not. Like moving light material around on your lawn, or when you already have a heavy implement hanging off the back. Especially working up hill running something like a rear mower or RC which is requiring power.