Some years ago, there wasn't a single (proper) organization without an Email Security Gateway. That briefly changed with the advent of good, cloud based, servers - such as Google and Microsofts. Briefly.
With around 320 000 000 000 emails sent every day across 5000 Million mailboxes, companies still rely on Email as their number one form of reliable communication. You can "talk" using virtual calls (such as Zoom) and IM tools (such as Slack), but you cannot send a proper message - Complete, traceable, and meant for all types of recipients.
Companies lived fine with email - They would host their own email server (exchange, usually), add an Email Security Gateway before, maybe a firewall and an endpoint Antivirus to every employees' computer and things seemed to work fine.
But something changed: With the great shifting to the cloud, and in particular platforms-as-a-service such as O365 or G-Workspace, companies decided to abandon they're datacenter-based email systems. Apparently Spam stopped being a problem.