Good question. Keychat uses ecash sats as stamps for messages. Users do not lose privacy due to payments, and relay servers no longer need to rely on advertising models to make money.
Onchain sats and LN sats cannot achieve this, making it the most suitable application scenario for ecash sats.
nostr:note1h895va2vdwscyl3r339pdwnvy83kdu0cl646dnal69ws2n2s6p2qx2gaaz