Embarrassingly I must admit that at one point I was one such person. I can tell you why though. As a n00b if you wire something wrong and your circuit is starved for current things might not get damaged and you have a second chance to make things right. If you're using a beefy supply and screw up you open the valve on the magic smoke. Adolescent instinct says if that didn't happen last time it must be the current that made the difference. Not true of course, it just made your mistake more obvious... and permanent.