If the direct fee and subcontract fee are applicable on the defined cost. What is the equipment over head, design overhead and people overhead used for - would this not fall part of the direct fee?
No, these three make up Defined Cost and are intended to avoid the need for the calculation of minutae when compensation events occur, so
the percentage adjustment for listed Equipment is normally a negative percentage adjustment from a standard list, thus avoiding the need to justify (argue over) the costs of Contractor owned Equipment as well as produce an invoice for hired in Equipment;
the percentage for People overheads is to avoid the need for calculating the on-Site minutae of the costs listed in People 41 of the Shorter Schedule of Cost Components;
the percentages for design overheads is to avoid the hassle / complexity of calculating design office overheads on top of what is paid for an individual designer working outside the Working Areas.