I'm not going to mod my car (well, not poor thousands of dollars into engine parts and interior/exterior modifications). If I want something faster, I'll buy something faster. And I cannot dog anyone for choosing modding as their hobby. If you have the money and really enjoy it, then more power to you (I don't have the money).
I like having a good looking car, but I'm a racer at heart. I can't see spending money on your car unless it's functional and there's value in it. But honestly, where do you spend most of your time when it involves your car? Behind the wheel. And to me, how the car drives is more important than numbers and looks. It's really all about communication with the car and yourself (for me at least), and out of the box, the Focus is a pretty intimate car. It lacks power and a good shifter, but the suspension and steering are excellent for stock.
When I'm driving down a nice bend, an on-ramp, or autocrossing, I'm not thinking about how my car looks, the warranty getting voided, or how much I'm shortening the life of my car. I'm only thinking about how much fun I'm having and every time I get out of my car after something like that, I always turn around and look at it to say, "Gah, I love my car." Basically every time. Strangely, it puts a smile on my face, and my monthly payment and the hours I spent working to pay it suddenly seem worth every penny and minute.