You can code from anywhere, but typing out code isn't the only part of software engineering. Understanding exactly what code the business needs, and how it interacts with the rest of your company's environment, can be more difficult if communication flows less freely.

If engineers are purely sitting at their computers and not talking to each other at all (except during scheduled meetings), the team could probably be converted to remote without downside, but plenty of organizations have an implicit dependency on unstructured conversation, and while there are ways to facilitate that in a remote work environment, it's not obvious.