Because SQL Server 2008 R2 is unsupported, Microsoft no longer provides it via regular channels. Possible legal sources:
When Microsoft released SQL Server 2008 R2 in 2010, it was considered a substantial "minor" release. It bridged the gap between the initial 2008 release and the upcoming SQL Server 2012 (Denali). En Sql Server 2008 R2 Standard X86 X64 Ia64 Dvd 521546
SQL Server 2008 R2 Standard is a relational database management system designed for department-level applications and small-to-medium business environments. While it is a legacy product that reached its , it remains in use for maintaining older systems or specific compatibility needs. Because SQL Server 2008 R2 is unsupported, Microsoft