Compared to areas of low pressure, why do areas of high pressure have fewer clouds?

Because evaporation and condensation doesnt reach that far due to the atmosphere.

Cause of he different elevations  hope this ?

So  if  the sum of the enthalpies of the reactants is greater than the products, the  reaction  will be  exothermic.  if  the products side has a larger enthalpy, the  reaction  is  endothermic. you may wonder why  endothermic reactions, which soak up energy or enthalpy from the environment, even happen