Perhaps one of the differences would be licence type? An instructor with a CPL may be considered to be less likely to be deriving pleasure from the flying and, as a commercial pilot with a qualification specifically designed to earn money from flying, it may be considered that currency is not an issue.
The same however, might not be considered with a PPL holding pilot. So, in these cases, it would be interesting to know the licence type.
Cheers
Whirls