According to science.howstuffworks.com the reason most of us sing in the shower:
You're in a warm, small, safe environment. You're comfortable enough to be in the buff! Stress literally washes off you. When you relax, your brain releases dopamine, which can give your creative juices a jumpstart.
Not only are we comfortable their but it's the closest most of us will ever get to the recording studio. Shower acoustics add some extra bass to those who like to belt it out in the buff.
Singing in the shower is great for solo performances and you may even be able to pull off a duet, problem is it's hard to fit four or more in the shower.
Finding the right space to sing is a game changer, and this family may have found a hidden recording gem on their farm.