Without the invention of the mouse, we might all still be using trackballs. A mouse to me is not an "A ha!" invention. I remember when I first used one that it seemed silly to move a trackball around upside-down like that.
And without laser printing, we might all still be using ribbon cartridges at work, because of time/cost concerns with inkjet.
Everything that happens can have profound effects on the future. Think of the Challenger and Columbia disasters. While it's true that the American public had somewhat lost interest in the shuttle program prior to the Challenger disaster, they didn't think of it as risky or dangerous. Think of the lives that would have been saved and how much farther along we might be in space exploration had greater precaution been taken.