D&D 5E - Why is there a limit to falling damage?

This came up in game when a player whose PC was a barbarian came to gorge 1,500' deep and said, "Yeah, I'll just step off."

I asked if they were committing suicide, because this was going to kill the PC. "Nope," the player replied, "The barbarian will survive the fall."

I stated unequivocally the PC would die - yes, I was aware of the rule - yes, I guess this is a ruling outside the rules, and therefore, a house rule that was unannounced. However, I countered, the player was exploiting player knowledge of the rules to benefit his PC.

So, that's where this question comes from - what purpose does the limit on falling damage serve? What am I missing?

I do remember the falling damage rules debates from the early Dragons and the subsequent ban on articles and letters on falling damage. Just reviving an old D&D tradition: Let's debate falling damage!

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