The base, lattice, or ggplot2 plotting systems make it possible to create all conceivable plot types, either quick and simple, or even utterly detailed and sophisticated. All these systems have their own features and peculiarities. But they also have one thing in common: the relevant plots are all purely static.
In particular, the ubiquitous use of the Internet and corresponding browsers make it possible to easily share interactive content. Interactivity, in turn, helps humans to better understand the contents by actively interacting with them. Interactive charts are, of course, a great improvement, since viewers can play with the displayed data, and thus discover possible coherences and differences among other things to get a better understanding of the shown plot.