The saying goes that "Necessity is the mother of invention," but, is it really? I would argue that laziness is a stronger reason for it.
Let's go back to that very first invention, the wheel. Up until the time he invented it, Oog the caveman carried everything he needed in his arms or on his back. There had to be a point when he said, "I'm really tired of lugging all this stuff. There has to be a better way to move it!" It wasn't necessary, but it sure would make his life easier.
So it is with all the advancements of civilization...
"I'm tired of telling the same story over and over" and so we invent written language.
"I'm tired of copying these books by hand" and so we invent printing.
"I'm tired of making a fire to cook" and so we invent stoves and ovens.
"I'm tired of walking and I'm tired of taking care of the horses" and so we invent trains and planes and automobiles.
Think about all the improvements that are made in everything we use. They're all designed to make our lives easier. And why do we want things easier? Because we are lazy!
Of course, there are some inventions that don't fit that category, ones that appear to have been created on a whim. As my son Chuck has pointed out, the flamethrower seems to have sprung from someone saying, "I'd really like to set fire to that guy over there!" Then again, it could just be that the inventor was too lazy to walk over with a torch.