Masters don't cry!
Trying to avoid showing any signs of weakness can be a strong temptation for a dominant. It's sort of implicit in the job title - "dominant" or "master" - that there's a certain amount of strength, fortitude or resilience involved in being one. But all strength has limits. All iron bars can be bent, so why hide the fact that this is so?
There are a number of reasons why a dominant might not want to put their limits on display...