From someone who worked in aviation for 10 years and then moved into 'elf and safety' this is only my humble opinion.
Every health and safety training course i've ever been through (there's been a few too) PPE is classed as relatively low down in the hierachy of control. However PPE is always an easy thing to put in place and easy enough to manage but will not necessarily eleviate the hazard, compared to processes and procedures which in turn are somewhat harder to manage.
hierachy of control goes something like this:
Eliminate
Reduce
Isolate
Control
PPE
Dicipline to follow the above