Because it makes model creation easy--and if you can build a good model, you can sell your good model.
It's intuitive, easy to figure out, easy to navigate. One has to avail themselves of all of the tutorials out here (Gary Miller's and EZ's in particular taught me a whole of lot what one needs to know), but once you see things explained, then it becomes easier.
The trouble I run into is thinking of something to build that is beyond my current understanding of the program. Eventually, I'll figure out how to do it.
The only critique I have of the program is that there needs to be a little bit more interactivity with the menus and customizing the custom tools tab. Other than that, I love working with it. I tried Caligari's "True Space", but you need a degree in physics to learn that program, the learning curve is that steepl