Could someone explain the pros of deleting (or keeping) unused code?

Question

I have heard many times that unused code must be deleted from the project. However it is not clear for me \"why?\".

My points for not deleting that are:

Answer 1

This discussion is several years old, but I just ran into it...

One thing that I did not see mentioned is the work that must be incurred to remove the unused code. In many cases, the time and effort to remove the unused code is not trivial in nature, plus there are typically additional costs to test and document the refactored system. Just another thing to consider in the decision process.