LA has a light problem. I don't live in LA, but I have driven there: Why wouldn't they put green arrows to let people waiting to make a left go first? After tho

LA has a light problem. I don't live in LA, but I have driven there: Why wouldn't they put green arrows to let people waiting to make a left go first? After those people go, then traffic can flow as normal. I remember the light kept turning green, with no green arrow, and I had to keep waiting and waiting until there were almost no cars. Had that left arrow been there, this could have cleared up traffic along with the 20 cars waiting behind me to make a left as well.