I can defiantly understand why they want to auto-update older sites. Safer net and all...

But, as previously mentioned, I prefer to update my site by myself. To control to update process and monitor the issues/bugs.

And also, some agencies get payed to update sites for their client. This auto-upgrade can potentially break sites and many client will blame those agencies instead of the auto-update process or bad plugins.

Updating major version is a process involving backups, staging environments, testing and more... I'm not sure WordPress will do it in core.