Gov don't move because it's not worth the risk for people with decision power. If you succeed, there's no big win to tag on your resume, if you fail (the most likely to happen) you're out.

Moreover, the people working for the teams that should make the migration usually don't want a migration, so you have to perpetually convince them of the future gains.

For the last 10-15 years, very few revolution have been made in gov ICT. Most of the job is usually rewriting existing app in a recent language or creating apps for not critical features.