They do get to offload a lot of the work to the graphics chip, which undoubtedly helps, but they're also expected to perform compositing now, and typically to include all sorts of extra graphical effects. On top of that, as h111 mentioned, we have all these interpreted languages and VMs (such as Dalvik), and all the work done by modern web browsers to handle fancy interactive websites.
It's the price we (or rather, perhaps, the typical consumers) pay for prettier graphics and easier software development.
[looks at their website]
"Provide[s] exceptional service to [their] valued customers"!
What does that mean? I hate it when websites do stuff like that.
"You can't make a program without broken egos."