Many 3D Creation tools have added these features in one way or another. Zbrush, Blender, even Rhino (since version 7.0 with the Quad Remeshing tool) have tools that allow you to quickly reduce the amount of polygons on a mesh. The main issue with this approach is that the result is not 'clean'. So in some cases texturing or modifying the asset may be more difficult, and the result is possibly not as optimised as it could be.