Why did Jon Keynes believe interest rates do not affect consumption in individuals but do in business men?

The interest rate in the Keynesian model is a factor determined a demand for money which uses for investment which is separated from the demand for transaction which depends on income.Everyone with income is investor or business man.But to solve the simultaneous equations, interest rate will determine GDP, called IS curve.And GDP minus taxes determined consumption and saving. In reduce form, consumption depends on interest rate as well.