Excellence increases demands. Critics gather to spot tinier flaws as work nears perfection. Promptness invites impatience. In correspondence, the faster you answer a letter, the faster your correspondent will answer giving you something with a shorter deadline. This reaches a fever pitch with electronic mail.
Skills diminish professionalism.
Engineers who admit to drafting skills are vulnerable to assignment of drafting work, just to help out. Similarly, female professionals should hide any clerical skills lest they be asked to pinch hit for one of the secretaries in the event of illness. What separates the competent from the incompetent is the ability to cover up mistakes. Many successful sales demonstrations have been made with defective products in the hands of competent persons who avoid demonstrating the features which don't work. Beautiful Xerox copies can be made from originals riddled with correction fluid.