The dopamine production in your brain can become dependent on the Adderall. Reaching this point would make you "that fucking addict" in your local community.

my guess would probably be not wanting to develop a tolerance, potentially because it isn't prescribed and is then probably expensive...

I highly recommend you try not taking Adderall. In my experience (I've had plenty of experience), it only screws with your priorities (you think you can do anything while you're on it) and makes you completely useless when you're not taking it. I was prescribed it myself for several years, and only recently went off. I've replaced Adderall with a little bit of caffeine, and lots of exercise. And yes, Adderall has a bunch of negative side effects. Try it once if you want, but don't make a habit out of it--you'll regret it long term.

I actually found myself quite annoyed by distractions. I felt like I was God, and I wanted to get my project done as soon as possible. Felt wonderful.