I have a trail cover. I use it to cover the Jeep at night when the Safari top is on, or no top. Especially when camping. It keeps the dew or rain out of the inside of the Jeep. The trail cover fits over a bikini top. I also have a soft top. The trail cover will not fit over the Jeep with the soft top up. I tried that and failed once when I wanted to leave the windows off over night.
So, your question as to why you would need a trail cover if you have a soft top? Answer: You wouldn't.
But, if you are camping or something with your new bikini top on, you would want to have the trail cover with you.
Edit: That's a good deal for all that stuff if they are in good shape.
ok That is what I was worried about with the safari top on. I didn't know if it would fit. It does work with the doors off right?. ALso yes they are like new , I actually wonder if he used the trail cover ever.