A very large proportion of people in the UK have access to the Internet - even if many of them choose not to use it.
The BBC have announced that Ceefax will be closed in 2012. Audience numbers have been falling over the years.
For any organisation (e.g. an airport) to provide a Teletext data feed costs money to keep it going and reliable.
Are there really enough people out there who want arrival times on their TV instead of their PC for Gatwick to consider it worthwhile ?