Not always the standard
For centuries, brick sizes had remained relatively unchanged.
Then in 1784 brick sizes in the UK suddenly increased when a cash-poor government placed a tax on every thousand bricks used. Unsurprisingly, it didn't take long for some crafty brickmakers to make larger bricks - to reduce the tax.
The government soon responded by regulating brick sizes and doubling the tax on anything larger. Brick sizes very quickly returned to the standard!