1. backward compat. most still use commonjs over ecmascript. some even use amd bundles. 2. design by committee. most large projects have users that have edge c

1. backward compat. most still use commonjs over ecmascript. some even use amd bundles. 2. design by committee. most large projects have users that have edge cases. devs sometimes create messy apis just to cater to a larger group of audience. notnecessarily bad, sometimes the product just grows, sometimes its for security reasons. 3. incompetence. sometimes you dont need a library. sometimes their implementations suck in terms of readability, security, space and time complexity, maintenance. 4. code golfing and not using linters. these 2 are pain in the ass.