For reasons not yet clear, Steam has become inaccessible in Vietnam.
One potential rationale for this unexpected action, highlighted by Vietnamnet.vn, is the concern voiced by Vietnamese game creators regarding the challenges of contending with the vast array of games from around the world on the platform. Local game producers must navigate through governmental sanction processes, while such scrutiny is not required for foreign titles.
GamesIndustry.biz has also suggested that the prohibition might be related to issues concerning "Valve's business practices."
At the moment of this report, Steam has not provided a definitive explanation for the restriction of service in the area.