Why do people have such large trailers?

You get and use what fits your needs at the time. In my life I've spent least 6 months in a bivouac bag or less backpacking in wilderness areas, or bicycle packing through Europe. That's what I call camping. I've spent another year plus in larger tents over the years in campgrounds from coast to coast and again in various parts of Europe. Some of this in quite remote "camping" spots, some in holiday camps that were not what you would really call camping. I've owned a pop up, small class A, and a couple bumper pulls, 1 an 18 foot box 1 a 24 foot box. Those were used from things like camping to base camps in populated areas to explore cities and the like.

Now I'm typing from in front of the electric fire, big screen tv playing the news, massage and heat going on the recliner as I listen to the rain fall outside. I just purchased this large rig to do my retirement travel in. Could we get by with smaller? Absolutely. Do we need something this big no... That said, we got it for the simple fact it fits what we want it for at this point in our lives.