Yeah, blame the one-eyed Jock (Brown was CoE at the time the rolling
25-year was stopped. So how can they bring back a rolling
30 that never existed?)
If you want a rolling 30, then move South, (not free, but reduced rate of €56 per year) but then get humped for every other tax under the sun instead. Swings and roundabouts.
It really doesn't matter who was in charge, when Ken Clarke introduced the concession in 1993(?), there were only c. 60,000 vehicles that qualified. Roll forward to when it was frozen and it was c. 320,000 cars. It was becoming a bit more than a loose-change give-away.
ETA:
It's still cheaper Mark, before Brown introduced the lower rate for cars under 1550cc, it used to cost £150 a year to tax the Banana. Now it only costs £130, and in real terms much less.