I do the "random for fun renders" for a couple of reasons.
1) I sit at my computer, working on BTW for 12+ hours per day, 7 days per week. Sometimes, I need a break from the story side of things. So, I'll make something NOT directly related to BTW. Most of the time, it's just a 4k shot. Sometimes, it's an animation. Either way, it's a break from the story.
2) I use those renders, both still and animated, as a way to test my limits. ESPECIALLY the animations. It's how I push myself to learn more, get better at doing them. They are the reason that with every chapter, the game looks better and better.
So those random renders are actually quite important