A PA's role is different from a normal employee. They are hired to help the Boss, it may be both official, as well as personal. Personal like keeping track of his Bank accounts, car servicing, purchases, school fees of his children, maintaining files of the Boss insurance policies, payment of premiums, etc. This is because the Co wants the Boss to be taken care of in all these, so that he can work for the organization without any personal problems. The normal employees do not do such personal works of the boss. You may think the PAs don't have any work load, whereas they may doing all the above mentioned works, which you may not be familiar with. In addition, they may be doing some official works as well, as assigned by the Boss, like making his travel arrangements, co-ordination/followup with other Departments, etc. Whether they are good/efficient in handling all these activities or not, is best to be decided by the Boss only.