Funny that I'm also in Springfield and faced this issue. I didn't think it was such a common name.
Key reason the Simpsons live there - it could be anywhere.
Matt Groening grew up in Springfield, OR (also Portland, the streets names sharing a lot of character's names), it was only after he placed it in Springfield that he realized Springfield could be anywhere. He apparently makes direct references to local landmarks and establishments, and certain characters are rumored to have been based off of locals.