I feel the same gut reaction when I see projects like a cyber deck, or people building old pentium computers but I also do the same thing, I seem to keep rehashing things (variation of a note taking app). Only thing I can think of is the joy of doing it.
Expanding further, it's easy nowadays to get a pi and attach some HDMI screen to it and battery source. Gets the job done, do I need to personally write a graphics driver for it to be impressive idk.
In the long run I am trying to learn harder things though so my skills are not commoditized.
This is the second post today I've seen here that is a complete and utter waste of time and effort, and I love them both. People make things for the joy of it. Constraints breed innovation and creativity - this is a perfect example of someone doing something stupid purely for the joy of doing it and it's wonderful.