I think it's important to remember that unions are not allowed to campaign on behalf of others - so however much teachers want to support anyone else facing a later & later retirement, it is not legal for the NUT to say that. They are only allowed to ask for support for their own members.
How people age is vastly different. As there is less credit/money around, it is the vulnerable who suffer. Older workers, chronically ill, very young, people with handicaps etc etc. It may be illegal to discriminate, but by saying that everyone HAS to work to age 70, a not-so-fit 65 year old is being pushed out without full pension. It's hardly someone's fault if they need a hip/knee replacement etc.
We do seem to be returning to the days when people worked until they were close to dropping, then relied on family to house & support them. Yet for many of us, we live miles from family and have young kids, mortgages, no spare rooms etc, even if we want our aged P's to move in with us.
The idea of 'deserving' a good retirement is a bit of a British utopia. Here in the US, people assume that they will work til they are late 60s, then do something part time etc as they just don't have the concept of retiring and having a 'holiday' for 20 years. They find it an odd notion. Pensions are less tied to jobs, so there isn't the concern about final salary etc. The majority of people I know just assume that they will 'keep busy' til they are too old/tired to keep going, then they will use their pension.