Just because students don't like to practice does not mean that they don't like playing an instrument. I always say that the rule of thumb for determining if a student likes music is what they do when they learn a song they like. Do they play it non stop? And I mean over, and over again until everyone is tired of hearing it? If so, the student definitely loves music!
I often equate practice to studying for a test. We don't like the studying part of the process, but we do enjoy the feeling of making a good grade. Learning delayed gratification is a tough process, but has lifelong benefits.