Because there’s someone else who would’ve loved to have worked twice as hard.
To have a job, to be able to work, especially these days, is a privilege. Nobody is entitled to a job, no one is promised a living. You have to earn it, you have to fight for it. So treat your work with respect, have pride and honor in what you do, no matter what it is.
What kind of a life is one where you don’t value your contributions to the world? It’s a waste of life, it’s a waste of space.
And if you really do hate your job, and if your work sucks that much, then quit today and start anew. Just remember that a job — work — is a huge opportunity to make a change in your life and that of others. Plus, you get paid money to do it. How cool is that?