Well it's a trend, and these don't always have rules, other than people follow them. Here are a few theories: is it's a refinement of the icon concept, taking

Well it's a trend, and these don't always have rules, other than people follow them. Here are a few theories: is it's a refinement of the icon concept, taking it to a higher level of abstraction. Possibly the reduced visual noise has a greater aesthetic appeal. Lastly I think the simplification makes it easier to see at a glance what the icon represents.