Great write-up on that subject is in the first chapter of "Mythical Man-Month". Here is small excerpt. Why is programming fun? What delights may its practitioner expect as his reward? First is the sheer joy of making things. As the child delights in his mud pie, so the adult enjoys building things, especially things of his own design. I think this delight must be an image of God's delight in making things, a delight…
And the rest of the book deals with why it is more often than not painful. In summary, it's complexity. Brooks argues that software, being a pure thought-stuff, is also the most complex thing we attempt to build. And it's even worse now than in his time with any concern for quality taking a back seat in the face of competitive pressures. So it's not really surprising that slapping together ever more complex systems out of ill-fitting, purely-designed components is not fun.