Proper documentation that explains what the code should do, how it does it, and if there are any known bugs is a lot faster (IMO) to read them to open a file to try and parse what the people who worked on it intended and what all its doing.
Add in cases where people go crazy with inheritance and you need it or else you have no way of knowing what all it is this new class can do.
Add in cases where people go crazy with inheritance and you need it or else you have no way of knowing what all it is this new class can do.