Why most of the world’s deserts are located in the western margins of continents in the subtropics?

In the tropics, moist air heated by the sun rises, sheds its moisture to give tropical mains. It then moves away from the equator. Where this dry air returns to the ground, it brings Almost no rain and produces deserts. Desert geography is controlled ultimately by precipitation physics. Sheer remoteness from oceanic moisture source may be dominating factor for the location of deserts in the western margins of the continents in the subtropics.