One thing that airline staff have been able to answer for me is why you get the piece luggage concept when flying to North America and certain other countries, whilst you only have the weight system on most other routes.

Certainly 20kg is nothing compared to two pieces potentially adding up to 64kg. Heck, with the piece concept, you get more luggage than some First Class passengers (lets be frank, the two piece limit is hardly a tough limit - if you really want to fit things in, just bring larger bags).

I'm guessing it's a regulatory imposition on the airlines, if so, what was the history behind it. A German friend said that Germans had to bring a lot of equipment to the US, so they needed large baggage allowances