Folks working with video often use several different applications (3D Studio Max, Cinema 4D, Vegas Pro, Premier, After Effects, etc). If you want to use something like Titler Pro (plugin), you can't do that with onboard graphics.
The clients we have that render a lot of video; they're running GTX-1080ti video cards.
For the casual user... not worth the cost. For someone rendering video 12-hours a day, easily worth it.
A video client in Nashville recently upgraded from an older hex-core machine with Quadro video card... to a 7900x with GTX-1080ti. What used to take an hour to render... now takes 15 minutes.
The CPU is obviously making a huge difference.
Very expensive machine... but this particular guy is constantly rendering video.
Any significant time savings means more earning potential.
Factored over a year, the time savings is enormous...