Some made-up examples:
- Architect's house is always crooked.
- Mechanic's car is leaking
- Chef's breakfast is as plain as boiled eggs
Is there an established saying for these situations?
"The cobbler's children are always the worst-shod"
is the saying I've heard most often to describe this phenomenon. Some variants are listed here.
I've always heard ...
The carpenter's house always needs work.
The preacher's kids are always the wildest.
One proverb is, "Physician, heal thyself."
If a barber has a good haircut...go to HIS barber.
People don't want to do for free that which they earn money for. The carpenter doesn't want to do carpentry on the weekends for free, hence his house always is in disrepair. It's human nature and I've seen it played out many times.
I've heard (from older folks): "the plumber's house leaks and the carpenter's house creaks". If I google that I get no results on it, so it must be very uncommon.
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