I don't think there is a wrong or right answer to this. For me it depends on the tune and the group of musicians I am emulating at the time...and thats part of real time arranging. If it needs a pad/ Hammond sound on the left then I use it.

as for the 'pros' who use left hand for mod/pitch wheel thats a different style of playing that often requires double tracking with your own prercorded accompanimnet track. So although you don't see them holding pad chords - they may have done so in prepeation.