I suppose we all want different things from the hobby.. Personally, ever since I was a little kid I wanted to create a model so real looking, that if photographed you couldn't tell the difference.
Also, considering the cost of models, I want to get as much out of each kit as I can. I also have a lot of junk in the basement that trains displace, so I consider every square foot as valuable real estate, again, trying to get the most bang for my buck..