I could think of a couple reasons: * bandwidth bill. * rich interactions without back-and-forth server trips. * What's on client-side can technically be save

I could think of a couple reasons: * bandwidth bill. * rich interactions without back-and-forth server trips. * What's on client-side can technically be saved on client-side. Thus, making distributed setup possible. And that contributes to lower bandwidth bill. * client hardware is no longer wimpy, why not use all those CPU cycles on users' laptop/iphone/ipad/android/etc.