On the face of it, loss of a cheap tool is no biggie. But, when you are in the middle of a project and right at the crucial moment, when that cheap tool seems indispensable, it suddenly looms large. Your project has lost momentum and you have to go somewhere and get one, costing time, gas, most of all, aggravation. It's the same with running out of the right size and configuration of screw. You might have hundreds of screws, but that special one costs impetus and you want to punish the material for the project out of frustration.