I read a lot of recipes online and a lot of them from the US ask for kosher salt. I see the need for Jews to use only kosher ingredients including salt. What I don’t know is why non Jewish people would specifically use kosher salt. Isn’t salt just salt?
Someone else can answer this much more thoroughly, but salt granules of different sizes have different effects on your mouth and the recipe. Kosher salt is relatively cheap large salt grains, so it’s a standard for lots of recipes