When I work on projects in my garage (cars, wood, metal, etc...), I like to be in a very good environment with comfort space (nice flooring, workbench, good tools, etc...). I believe the work environment is a reflection to the quality of your product and nice flooring is one of the contribution.
If I don't cover my concrete floor, I will stain it and make it really dirty, thus the garage is dirty. Therefore, appearance is one of the factor but I believe, psychologically, it affects the way you attack your project.
If you're a first-time homeowner and don't work in your garage much, you won't see the value in spending $500-$1000 (assume 2-car garage) to cover the floor w/ industrial-type epoxy. Just like storage space in your garage, you'll need to spend several thousand dollars to keep all of your stuff organized and be ready for any project.