Painting has become performance art. It's too bad Vine is shutting down, but we have Instagram clips, Periscope livestreams (now available on Twitter!) and of course, YouTube. Go to any one of these social apps and search #illustration and you're likely to find a number of clips and livestreams of artists in the process of creating.
Even digital painting apps are (at least partially) set-up to do this.
Here's my Prehistoric Fish drawing I posted the other day. After importing the drawing to ArtRage on my iPad, I took my Wacom Intuos Creative Stylus II, and painted it up while recording. Then, I emailed myself the file, captured it playing back in ArtRage, then played it back sped up in Windows Media Player, and recorded it using Windows 10's Win-G Xbox DVR recording capability. And then I did it again and again until I compressed it into 30 seconds.
Enjoy! Finished painting below.