Memory is just one kind of resources. Games do tons of I/O, often gigabytes/second. To illustrate, any PC game has a lot of places which call GPU driver like this:

    D3D11_MAPPED_SUBRESOURCE mapped;
    context->Map( buffer, 0, D3D11_MAP_WRITE_DISCARD, 0, &mapped );
    // Write memory address pointed by mapped.pData
    context->Unmap( buffer, 0 );

With C++ RAII, you can do something like that instead:

    MappedBuffer mapped{ buffer }
    // Write memory address pointed by mapped.pData.
    // No need to do anything else, the destructor of MappedBuffer will unmap.

This. Freeing memory is the least important job for destructors.