Fun and learning is a really good reason. It also reminds me of the damascene: trying to achieve something that doesn't feel possible, and working through all the extreme resource-constrained engineering limits.

I think most of my embedded projects aren't that useful, but they've taught me a lot.

I'm not disagreeing with you, I think this goes beyond impractical, it's doomed from the get go.

In my book, impractical means "I built a cuckoo wristwatch". Beyond impractical: "I built a cuckoo wristwatch but there was no room for a working mechanism".