I think an important part of agile development is pair programming. This way, information is shared with the team. Having two sets of eyes on your code can really increase software quality and shared knowledge.
It doesn't stop a lot of people from using it though. A quick search of Python code on GitHub for 'import pickle' shows almost 800,000 results: https://github.com/search?l=python&q=import+pickle&type=Code... And that's just public repos. Who knows how much it is used in private repos?