I think the issue is more that large tech firms can absolutely deal with external security in their applications. The amount of times gmail or Microsoft 365 has been hacked and leaked a bunch of client data is statistically zero when looking at their attack area.

Joe Dirt self hosting a mail server for his neighbors on a salvaged rack server is 1000x more likely to get hacked or lose a ton of his neighbors’ data than a big tech firm.

That is kind of the trade off for community hosting. There are very very few backup and security-literate people in communities.