Certainly you would not expect an educated gentleman of proper breeding to distract himself with all sorts of mundane trivialities, that could be prefectly well handled by a more servile person. Thus unburdened he can focus his superior intellectual resources at duties of importance.
Also, leaving items for private purchase is not to be always taken as an indication of thriftiness on behalf of the crown. Commissioned gentleman of proper education should be trusted to pick the items of equipment and uniform most suited for him to carry out his appointed duties. However, in the case of other ranks, lacking sufficient breeding and judgement, it may be necessary for the crown to exert closer control and issue items directly.