Bright colors in McDonalds was psychological marketing in action. It attracted children, but being around bright colors for more than a short period made adults want to leave.

Or, come eat; then leave. McDonalds didn’t have adults sit and talk over coffee for hours. People came, ate and left. It wasn’t by accident

Now contrast this to any coffee shop, or bar, where people sit and chat after a meal. There is a reason for everything