Our hobby is multi-faceted. Ask 100 enthusiasts what they love about it and you're likely to get 100 answers. Here are the hobby's two biggest highlights for me:
1.) It requires several disciplines, which appeals to my sometimes short attention span and desire to learn new things. I came to the hobby most interested (and experienced) in electronics, and am now captivated with track planning and scenery. In model railroading, you draw, assemble, paint, sculpt, build, and "hack," and you have to do at least some of these things well.
2.) The focus in our hobby is on modeling times past, which has a powerful sentimental pull for me. Frankly, I'm one of those people who was born in the wrong decade. 100 years ago, America was en route to being on top of the world. The overall societal tenor was of enthusiasm and looking to the future. Most of us didn't specialize, but knew how to do different things in addition to our chosen profession. Our money system was pre-fiat and based on tangible value, as were our attitudes toward children, neighbors, and self. I think about these things extensively when I watch the trains run.