4) How about Serum Swap?
Well, it's *less bad*:
a) gas fees of $0.00002
b) 1 second settlement, so arbs should happen closer to market price
but IL is still there.
5) So why use it?
a) yield: it's a convenient way to drop tokens.
e.g. right now there's a 1,000,000 SRM airdrop on Serum Swap
b) New project: if you have a new coin and want initial liquidity, it's easy to drop it in an AMM.