Explanation:

Off shore Trade Winds : This is one of the principle reasons for the location of Hot deserts
on the western margins of continents. The trade winds blow in the North Easterly direction
in the northern hemisphere while they blow in the South Easterly direction in the southern
hemisphere. As such they blow over land and very dry thus no possibility of causing
precipitation.
Cold Oceanic Currents : The presence of cold ocean currents along the western shores of
continents leads to the development of high pressure over the water surface. This high
pressure leads to subsidence of air hinders cloud formation. This would be another
important reason.
Presence of orographic/mountain barrier : In case of hot deserts like the Mojave
desert(USA) where the Rockies and the Thar desert(India) where the Aravallis act as
orographic barrier to the rain bearing winds.