Even if the purpose was punishment, I wonder why we harbor such a deep aversion to corporal punishment.
The (US) Constitution prohibits "cruel and unusual" punishments in sentencing, but in my mind, losing years of one's life, which one will never get back, is significantly more cruel than, say, fifty lashes.
SCOTUS has said about the death penalty specifically that it is without a doubt cruel; however, it is pervasive, and therefore not an unusual punishment. Therefore there is no Constitutional violation. I suspect a similar argument in the inverse rules out corporal punishment. Fifty lashes, even if less cruel than decades in prison, is certainly a cruel punishment. It's also very unusual for 2017 America.
Prohibitions against X and Y unfortunately tend to be grammatically ambiguous. If your read it as "prohibited to do X and prohibited to do Y" rather than "prohibited to do [X and Y]", then it is equivalent to "prohibited to do [X or Y]". So for example, the statement "It is prohibited to bring fruits and vegetables across the border" would usually be taken to prohibit bringing fruits or vegetables alone.
Ok. We can argue grammatical pedantry all we want, I'm just saying what SCOTUS has said with regard to its interpretation of 8A specifically. There are three things not allowed: 1) excessive bail required; 2) excessive fines imposed; 3) cruel and unusual punishment. The application of a cruel but common punishment doesn't fit #3.
The (US) Constitution prohibits "cruel and unusual" punishments in sentencing, but in my mind, losing years of one's life, which one will never get back, is significantly more cruel than, say, fifty lashes.