It's not that easy... Moving a factory isn't free, nor does it happen instantly. And at some point, you're also running out of impoverished countries to move to, especially if you also want them to be politically stable and come with the infrastructure you need.

Plus, this being VW, a German company, half of the board seats is held by union representatives, and a significant portion of the rest are held by local politicians (the state is a minority shareholder in VW).