Osobně jsem to taky zatím nezažil (nepoužívám MS účet, vím ale, že si na to uživatelé někdy stěžují), ale našel jsem tohle:

Automatic device encryption is only supported when the system meets above HW/SW requirements, and also satisfies the Modern Standby specifications with:
- Solid-state storage (SSD or eMMC)
- Non-removable (soldered) RAM
- Windows 10 Version 1703 (Creators Update) or higher

BitLocker automatic device encryption is enabled only after users sign in with a Microsoft Account or an Azure Active Directory account.
BitLocker automatic device encryption is not enabled with local accounts, in which case BitLocker can be manually enabled using the BitLocker Control Panel.