What is the fundamental problem with managing computers in stand-alone Windows workgroups?

In a workgroup each computer maintains its own isolated local Security Account Manager (SAM) database. Because there is no domain controller acting as a shared authority, a Security Access Token generated by one machine carries local SIDs that other machines have no record of and cannot validate. This forces administrators to duplicate identical user accounts and passwords on every machine, which is the core management burden of workgroups.

SIDs are generated independently by each machine's local SAM and remain local - they are not transferred to the workgroup or to other machines during a workgroup join.

Joining a workgroup does not prevent a machine from later joining a domain; a domain join simply replaces the workgroup configuration with domain membership.

The inability to accept tokens from other computers is a consequence of the decentralized SAM architecture, not the root cause - the fundamental problem is the absence of a shared identity and trust authority.