Why the foundations are placed below ground level?

The load has to rested below groung level  so that loads of the structure is distributed 

thanks for the invitation

  To face the subgrade reaction (straining soil

The foundtions are basically to divide the loads of a structure to the soil

because it`s working to send all the building load from all the members through the coloumns to the soil at last stage

to send all building load to orignal and rigid layer of soil