While they do pop out occasionally, they spend most of the day sleeping ... a lot. They sleep for up to 18 hours. Every time you see Sonic running in the brightly lit daytime forest, he's probably groggy, cranky, and in need of a nap. And he wouldn't be so nimble, and would just stumble around. Imagine how you'd feel if you had to wake up at three in the morning to run loops and collect rings?
2. Hedgehogs Can't Roll Very Fast