Sure there is. Email is an open standard, enabled by other other open standards. Things like authentication and service location are dictated by implementation. As a user, I can email anyone on the planet and retain those communications. My employer retains some email dating as far back as 1992, in native format.

Chat is almost always a closed loop. There are usually large implementations, and as a user I can only message within one. There are some exceptions to that. Chat always gets kicked around as corporate strategy changes. At work, I’ve probably used a dozen incompatible Microsoft solutions as their strategy meandered around. Jabber was the big attempt to make chat like email, and it failed.

Email still runs the world, despite its many flaws.