Your students will practice when you start telling the truth.
The Faculty Handbook

I don't enjoy drills.
However, I'm acutely aware that the quality of my musicianship depends upon major/minor/blues/Byzantine/Algerian scales, arpeggios, and octave practice along with ear training, sight reading, and theory review, and so I do my drills.
Ugh.
I do it. But I don't like it. I never regret it afterwards, but during it—man.
I don't like that my neighbors can hear me mess up. I don’t like that my mail lady can hear me curse. I don't like that I can't make my muscles instantly do what I command and instead I have to put in hours of concentrated repetition to get it to feel natural. I don't like that my sightreading is not as stellar as I’d like (on the clarinet, I am a sightreading master)(mistress?)(so why not on the piano?).
The truth.
Students are so shocked when I say this with passion and enthusiasm.
What?!? But…you're a teacher! You hate drills?
Yeah, my guy, I'm just like you. My teacher assigns drills and I don't like doing them.
Whaaaaaat?
Suddenly you're less…Authority with A Capital A…and more…a human person.
Show them the you that's you.
There's a piano teacher I highly respect. Chloe.
Chloe detests JS Bach. This blows my mind because a. I really dig Bach, and b. she sounds AMaZinG when she plays his pieces.
Just ‘cause she doesn't like it doesn't mean she can't do it. She can play it, and then some.
But she's making snide comments under her breath the whole time, and that's comedy when you happen to be in the know.
It should be no surprise that her studio has a wait list.
We do the work and study the not-so-exciting stuff because the struggle, the push/pull of learning how to master superb technique—that energy shows up on stage.
When I know I'm loose, well-rehearsed, in the zone, and know my stuff, then the performance has very little anxiety surrounding it. I can be fully present. It's a releasing of the soul, a party involving the cells of everyone involved and stimulated by vibrations of pleasure.
But to get there, I know I have to do the things that are not so exciting when I'd rather be doing anything else. And *controversially* I have no issues complaining loudly about it, and I do so with relish.
And the reason why I don't mind complaining is I will do the work. I am not lazy, I grasp difficult concepts easily and am willing to put the effort in to get the results I want.
Most just complain and then maybe they might sort-of practice so that they can say they put in the time. I'm complaining while I am giving it everything I have to be the very best I can be. We are not the same.
Tell them that and be seen as human.
Tell your student you spent [x] hours learning how to do [a one measure passage] to look cool when you're with friends and happen to walk past a random piano.
That's OK. Why don't we share things like that?
Tell them that you began learning an instrument because [insert actual reason, not the story you tell at job interviews].
That's the kind of thing that makes students practice. The truth.
We hold back so much of our love for the art trying to maintain a certain image.
Why?
Be professional, of course. Be appropriate, of course.
Tell the truth, though. Let the truth be your image.
We teach this.