That being said, if I send you a message, it's because I'm interested in you. You have struck me somehow. I don't send a message to every "match" on here because even if we are 99% by their standards, what you write on your profile might make me feel different.
So if I send you a message, it'd be nice if you sent one back, even to say that you aren't interested. It's the internet. There can be absolutely no repercussion for that, and plus it would just be polite :)