In the US, palm oil is not a domestic oil, it's one that comes in chemical tankers. Petroleum & fuel tankers are too gross, those materials may be in the same

In the US, palm oil is not a domestic oil, it's one that comes in chemical tankers. Petroleum & fuel tankers are too gross, those materials may be in the same terminal, but not the same ship as palm or tallow. And they don't need to fully remove every last bit of diesel after discharge for instance before loading gasoline. They fully clean out the heavy fuel and crude carriers far less often, compatibility is usually acceptable. Ship tanks are just challenging to get really clean, depending on what has been in them. Those developing plantations & ranches are in countries where they need our industrial chemicals, and we seem to consume their products in similar bulk. It could be considered an uneven exchange, but that's what intercontinental commerce has been for millennia. While shipbuilding has been largely motivated by profitmaking according to value differential, buyers and sellers are both making money so they're accordingly influential. These are the chemical ships where they have to clean out most compartments after cargo discharge anyway, so they can load something different for the departing voyage. Chief Mates love it after they have discharged things like Benzene or Methanol in developing countries because they leave the cargo compartments and maze of on-board pipes & valves cleaner than any intentional procedure. And pure chemicals like this just evaporate. They know they can load almost anything after that.