Because it pushes you to try harder at the things you do like. It drives you to accomplish your dreams and to keep moving forward with the career you really want.
I understand hating the alarm clock, waking up early and cursing my job for keeping me tied down when I have better things that I'm meant for. I understand hating the gigantic time suck that takes away from your dreams.
(Even as I'm writing this, I'm getting handed more and more paperwork that I have to get done as quickly as possible. Yes, I'm writing at my day job. It fuels the work I actually want to do.)
It's really hard to keep your head up when outside factors take chunks out of you.
But it's not what you see for your life, and it won't be this way forever.
Focus the energy into more production. Wring what little time you can from the spare moments you have to work smarter.
Read and Study when you can. Learn from the greats who've made it. Then go and do what they did.
Let your disgruntledness be a motivator, a reason to work harder to make your situation better. You might find that it urges you to accomplish more in a shorter period of time.