Functional programming is hard, it's hard to have pure functions which don't mutate anything in a system, there's always state somewhere. Businesses also like

Functional programming is hard, it's hard to have pure functions which don't mutate anything in a system, there's always state somewhere. Businesses also like to isolate and manage their state in certain areas. OOP more accurately reflects this. Although functional programming is becoming popular when scaled-out, take for example lambda functions or docker containers, which generally don't use state and nicely suit the functional programming paradigm.