I guess as a typical engineer (not CS person type of engineer or software engineer) it is easy to think that. One might be working with machines or buildings and so on, all which require _calculation_ of processes. Those are typical cases for "just write a correct function", possibly one that takes many things into account. For such scenario OOP is truly useless and only over-complicates the matter. However, when we get to simulations, where maybe there is no known formula, or the precise calculation would be too expensive, then OOP can make sense. Doesn't have to, but could.