We have internal conventions to always camelCase field and collection names, but developers are prone to forgetfulness and honest mistakes. As per Murphy’s Law, anything that can go wrong will go wrong.
Without an enforcement mechanism, snake_case, PascalCase, UPPER_CASE, Space Case, and other strange cases are bound to appear, and once they get coded throughout the system, they become difficult and time consuming to fix. Each individual occurrence doesn’t have a hugely negative impact by itself, but when they add up over time, overall they become a significant barrier to readability and increase mental burden (worst of all it just ain’t pretty to look at!).