Cause really, plants don't work too hard to grow. They don't have to try. As long as they get water and sun, it happens. I didn't have to try to become 6". It was part of my genes, and good nutrition.
And I can see the value in the good nutrition part of the analogy. If I am not well-fed, I can't expect to grow. And I suppose that the real work of spiritual growth is not something that I achieve (though I aspire), it's something the Spirit does within me. But getting good spiritual nutrition is hard work.
I hope I don't sound like I'm complaining, cause I kind of feel like complaining, but I really don't want to. It's that Romans 7 thing, but this time I've won. I have such a blessed and simple life!