Photorealistic icons [1] are much harder to parse, visually, than very simple ones [2]. In general, graphical UIs have gotten far more visually noisy in the past few decades. This has made computers much harder and more fatiguing to use. So often we seem to have “UX” designers changing things for the sake of change rather than undertaking the legitimately hard effort (UI studies) of trying to determine what will make the interface easier to use.
[1] https://1.bp.blogspot.com/_cTU5hVb22k0/R6u0lS9EFuI/AAAAAAAAB...
[2] http://cdn.cultofmac.com/wp-content/uploads/2011/04/Susan_Ka...