The rear entry door lets you.......
slide a kayak in the backdoor. my 10' long Compact Jr lets me slide a 9'-6" kayak inside, saving the expense and hassle of carrying it on the roof of my car.
and when I took the trailer to the fairgrounds for inside storage I was able to store the kayak at no extra cost.
and there is probably a bicycle out there with narrow enough handlebars that would fit in the backdoor.
I don't have a rock guard on my front window so when trailering I can look in the rearview mirror and see out the backdoor window at what's right behind me on the highway. I like that.