In other words, why are professionals/experts good at doing what they know to do for others but not for themselves ? What is the psychological bias behind this ?
Of course this questions comes from the popular saying which is only a saying, but for the sake of the question we'll assume that most professionals fall to this flaw. Dentists have poor teeth, doctors are fat, webdesigner have ugly sites, hairdressers have bad haircuts, masons have bent houses, etc
I read that the simple explanation is that they are humans like others and have flaws. But it doesn't explain why their flaw happens to precisely be in their field of competence.