That's not the point. This is all about NI contributions.
If one is in a position to (and allowed to!) top up an incomplete or missing year in ones NI record, each added year adds over £200 PA to ones state pension post-retirement. The cost of topping up a completely missing year is about £700, so the return on investment is around 30% - albeit deferred. It's hard to see how that could be matched any other way.
Under the old rules, one needed 30 years of NI to get the full state pension. I do have 30 years - but I don't have 35 years which is required to satisfy the new rules - except it now seems that only 30 of the years before 2016 will be counted towards the new rules (something which has been kept very quiet), and having opted out of SERPS (as was recommended practice at the time) won't qualify for the full amount anyway.
None of this might matter particularly, except that I stopped working in 2010 for personal reasons.