and its not for them to take you off the suspect list.... especially if you are the only suspect, put yourself in the shoes of the detective. Lots of people have gone to jail for crimes they did not commit.
And beyond that, its a fairly responsible action to take. There's no downside. If you never need it, it never matters. If you do need it, when the smelly brown stuff rolls down hill, chances are good it'll miss you with just a little record keeping.