In the real world Web we need to recognise several external factors:
- Due to the rapid development of Web specs ("the Web year")
the specs themselves may be flawed, ambiguous or over-ambitious
- Software has bugs (the cockup theory)
- Software vendors have their own agendas (conspiracy theory)
Together with local factors:
- Inertia / unwillingness to act as guinea pigs
- Licensing costs
- Support issues
- ...
