Overwhelming majority of volume comes from what looks like non-human blockchain interactions.
1) ARBITRAGE_BOTS
that profit from routing through different dexes
2) UNKNOWN_BOTS
which perform a lot of swaps, with unknown reason. List of all these bots in queries. It's under investigation. This category is accounting for 80% of total volume.
In most charts these were removed for clarity. Incentive for 2) choosing a dex is unknown and requires further work. Only 1 pool from every protocol is taken into account
Notably, AAVE drives a lot of volume. It's using Paraswap to swap underlying collateral for user atomically.