Expectation: "Our Information Management would be better if we could put all the documents in a single system."
Reality: "Documents are part of an Ecosystem and not a single place!"
SharePoint and other document repositories are great. They support records management features needed for critical content. So the knee-jerk idea is to put "everything" in there. Retire the file shares, force people to work a "modern" way.
This has been the orthodox thinking ever since everyone just assumed that everything should be in the cloud. Again, cloud is great. It is nice to not have to power your own infrastructure. BUT, it only works if you can get everything in there, everyone enjoys using it without training, and it performs better than what you had before.