canine:
Firstly, we should forget about rabbonim, since we can and should accept that rabbonim dress differently than non-rabbonim, and that that is proper.
Executives in Goldman Sachs wear suits while they are working, because nobody would do business with them if they wore black pants and white shirt like yeshiva guys.
I googled “why do bankers wear suits”, and the answer I got is that people like to think of bankers as risk averse, so they need to appear very conservative.