Because not everyone can do what they want to do and support their lives? I've hated every job I've ever had. I still have to do it.
edit: Why is it that you associate work with meaning in your life? What if someone find meaning in spending time with family, or whatever?
Well, I read it more as "if work is going to provide the meaning of your life, might as well have it be something you like to do." However, aside from the PWE, centuries of history tell us that liking your job is a luxury.
I find meaning in work because it's what I leave behind once I'm dead. What I create, build, and put out into the world is part of my legacy. That's pretty important to me, perhaps not the same for others.