Why aren't Japanese animation studios switching to digital art for production instead of pencil and paper? In the introduction paragraphs of Visiting Studio Colorido: Up-and-Coming Digital Animation Studio by Naoya Koji posted in October 2015,

[...]
Today, many of Japanese animation studios rely on “papers and pencils” to produce anime. Although some parts have been updated, this is the traditional Japanese style of the animation production which has been handed down for decades.
The world is now in the age of the internet and the digital tools. The animation studios innovate those new cultures, but Japanese studios remain in the world of “paper and pencil.” [...]

Even today, Japanese animation studios still use pencil and paper to produce animation.
Why can't they switch from that method and proceed to digital hand drawing for animation production since it is much less time-consuming? Why can't anime studios use graphic tablets (e.g. Wacom) to draw and animate instead of using pencils, papers, and eraser because it's maybe outdated and obsolete?
Here is an interesting article about how the anime production process works.

Here's an excerpt I found particularly interesting (and relevant!):


  [T]he crucial thing is that the frames are still initially drawn by hand, and no in-between animation is simulated by a computer. There are some animators who draw 2D animation directly onto computer, but in anime this is largely restricted to in solo animation productions rather than commercial anime. The industry prefers this because the animators are generally more comfortable and able with this method, and it allows easier checking and correction of frames under sometimes tight schedules.