MicrosoftAssuming one's own experiences in their particular circle of tech is the only experience in tech is a big mistake. Indeed, even talking to one's peers and direct customers is not the universal experience.
Having an on-prem Exchange server is a massive undertaking, requiring infrastructure to run it and somebody to maintain it. It makes no sense to use an Exchange server for that scenario when simply exporting to PST to long term retention works and is easy to train to even non-tech people. As mentioned above, Veeam uses PST as a container format for exporting data and mailboxes from both their on-prem and cloud backup tools. Microsoft's own Purview system uses PST as the container format for E-Discovery mail items.
But all of that is not even the issue. The issue is that the customer should have a choice. Switching the desktop Outlook to the web version is not for the customer's benefit. It is because Microsoft doesn't want to spend the money to support the older product.
