I don't have one but I have a small deck built alongside my fiver under the awning. Because...
1. Where I live in the fifth wheel is snake country. I spend lots of time outside just sitting and relaxing, daytime and nighttime. Snakes get the ground, I get the deck. Should one make it onto the deck, I can easily see it.
2. Had a skunk waddle through once. Glad I was on the deck! It didn't see me.
3. One night, sitting in a chair on the ground, I heard a mountain lion howl (an unmistakeable sound, btw). And I often hear coyotes and wild dogs. I cannot easily, at a glance, see what's under the RV. Being on the deck feels safer.
4. RV steps are tricky. I have fallen twice going in and out. I also have young grandchildren. The stairs and handrail I had built on the deck are much easier and safer for all of us.
5. It's a safe place to allow a pet outside and still be contained.
This RV stays parked as my home base. When on the road, I'm in my van. Yep, that's camping. I can understand why some might like the deck feature on a toy hauler.