Cause they probably don't want to feel like this mid session:
Super intense lighting can suck. Softer lighting can create a softer atmosphere.
Have you read a book/watched a sitcom recently where the main character is anxious or something?
You see a lot of people reference the "overbearing florescent bulbs beaming down mercilessly among them" when a character enters a medical establishment. Or even in TV shows, you hear the buzzing of florescent lights as an ominous tone.
The habit of replacing overhead lighting isn't present in medicine or the law because they are among the
impetus of the "ominous florescent lighting" trope (behind the office cubicle, of course).