What is "Worth It"
Playing an instrument does not leave you with a product. It is not a transaction of your time that returns revenue directly, as it would if you were paid by the hour. Since one can't be paid until one has practiced, the motivation cannot be about money.
When you practice, you don't walk away and feel better in a new dress, as you may after working out, and you may not be better at public speaking, as you would be after a speech class.
If you don't find a way to enjoy the act of practicing, then I would say you should take a break from your instrument. Music is meant to be enjoyed, and if you don't enjoy it, no one else will enjoy hearing you. Yes, it is work, but as with any work, if you heart isn't in it, your work will suffer.
Sometimes you will find yourself in an artistic rut, and sometimes in order to get back to your primary creative outlet you may need to explore other outlets. And that is ok.
It's "worth it" if you think it is. It really is that simple.