> Why this obsession with gelatin? What am I missing?

Probably just tradition. It's pretty easy to "accidentally" make gelatin when making a broth, and intentionally making it only requires heat and bones, which are essentially pure waste. Whereas agar is a product that you have to buy in a store, and wasn't even available in the West until somewhat recently.

Of course, everybody just buys gelatin in the stores these days, and agar is almost as easy to find, but old recipes tend to be handed down for generations.