Common User Access Standard.
The very first to start breaking the rules on a broad scale was - curiously enough - Apple with their we're-doing-everything-different-this-time iTunes programm. UI standards basically went steeply downhill from there on. We've moved so far away from standards that it can even take an expert weeks to get familiar with programms (s)he should be able to operate instantly. On top of that, the software manual has disappeared (I'm looking at you, Adobe)
Handling computers has gotten more difficult, no doubt.