Magic items are as personal as a bad programmer's "spaghetti code" - it's a creation without landmarks and roadmaps, and you need to be able to recognize what certain program loops do inherently just by studying them. You can usually read your OWN code, but how about someone else's? That's where a "wizard" comes in. Whereas the lay programmer might be lost, the true genius programmer would be able to dig through the mess and figure out what the heck the program does. Consider that the difference between clerics and wizards - one is trained for the activity, one isn't.