Using Lip Liner as Eyeliner?

Hi all! I have one or two lip liners that I am considering using as eyeliner- they are the kind of formula where they start out creamy and then dry down. I want to get more use out of them by using them as eyeliner, and I feel like in theory they would be perfect because they dry down and won't smudge, but I haven't heard of anyone else using them that way. Is there any reason why I shouldn't use them as eyeliner?