Instagram is genuinely good for street food. The photographs are the product, the audience is right there, and posting from the van at eleven in the morning takes ten seconds.
The trouble is what happens when somebody wants to book you. They send a direct message on a Saturday lunchtime, which is precisely when you are serving forty people and will not see it for six hours. Or they cannot find your prices, or your minimum numbers, or how far you travel, so they message three traders and go with whoever replies first.