Because people are to busy enjoying sonic games and think how hot he is, and even though he is 100 years old which is 10000 something years old, he will be faster than rd anything and will still look awesome, hot and young.:]
He turns 20 in Sonic Generations. But he still looks 15 and some people think that even though he IS 20 he still looks like he is 15. I don't really get what those people say really but I'm sticking with my opinion that Sonic really might be 20. please don't be mad at me cause I berkata that.