Personal email account uses:

1 - Transactional emails.

... that's it.

[edit] My other uses for email started dropping off around 2010 and were mostly gone by 2015 or so.

Business email account uses:

1 - Transactional emails

2 - Communicating with vendors and other parties outside the organization.

3 - Communicating with people who like email and are too high-up in the company to be ignored if they insist on using email.