[chriserin]

This happens with all languages and frameworks too. There are ASP.NET 1.1 apps at the last place I worked because when we did a test upgrade to 2.0 things started failing.... and there were no automated tests (yet a requirement of bugless releases :) so henceforth nobody wanted to invest in upgrading.

Its the nature of the software beast that upgrading a large and complex application to a new version of the language or framework is difficult and maybe prohibitively difficult. Once something is written and it works it often times stays as is... sometimes for decades.