I spent some time looking at voting systems, and also in attending a conference on voting systems 15 years ago.

Elections require a few things - one of them being transparency. Another is trust.

Thus while elegant mathematical solutions such as the one you presented, may be more accurate, they are also impossible for the lay man to understand. And for journalists to explain. For many this erodes the transparency,leading to mistrust.

This is the core reason why simple, but explainable approaches are preferred.