Why do Rocket don't go directly to moon?

Source : pixabay.com

The obvious reason is the capacity of rocket. Since we use conventional chemical propulsion system , even in space we relies on solar power & chemical power for our spacecrafts. Thus it requires huge amount of fuel to go directly to moon against the gravity of earth and of course sun. But in orbital motion , we are assisted by the same gravity to boost our craft speed to such level to be able to  the moon.

And also you would have to use propellant 100% of the time, rather than only during the standard stages of interplanetary transfer: launch, primary orbit insertion, transfer injection, secondary orbit insertion, and de-orbit.