It may seem bizarre to say so, but in some respects, medieval society was rather more civilised than our own. They hated waste in those days; objects were patched up or redeployed, very little was thrown away. And the same applied to people. Virtually no one, however aged or infirm, was without some role. Everyone contributed.

This attitude is part of a world we have lost, as was made plain by last week's House of Lords report on Britain's ageing population. The number of people aged over 65 is set to rise by 50 per cent, from 10.3 million in 2010 to about 15 million in 2030; five years after that, one in four of us will be over 65, and babies born last year can expect to live to their mid-90s.

To many, especially in politics, these figures constitute "A Problem" – older people as a burden as we wrestle with the cost of state pensions and healthcare for all these oldies. The Lords report wisely looks beyond this anxiety, arguing the need for changes in attitudes –more flexibility in business so people who want (or need) to work longer can do so, and a change in the sense of entitlement that makes people think that spending the final third of their lives in non-productive comfort is a basic human right.

But between the lines of the report is a story of waste, the kind that 600 years ago would never have been permitted. For some time, whether a person is struggling on state benefits, or is a grey-haired lotus eater on a sumptuous private pension, they are, at 60-something (and some earlier) widely regarded as having passed beyond usefulness. Society still sees retirement as a form of disposal – a sort of landfill for people. More than a third of women aged 60-64 and a quarter of men aged 65-69 may still be in work, two thirds of them part-time, but, for the rest, society has paid off the very people with the most experience and no small amount of wisdom. Golf, bowls, gardening, or day-time TV beckons.

Some do still contribute. About 30 per cent of over-60s help with voluntary organisations, two-thirds of pensioners regularly help an elderly neighbour, one in three working mothers rely on grandparents for childcare, and an unknown number are part- or full-time carers. The Lords report quotes Age UK's estimate that people over 50 make an unpaid contribution to the economy of £15.2bn a year, of £3.9bn in childcare, and £5bn as volunteers.

At this paper we know about this "work" of older people because of our Independent on Sunday Happy List, the annual project in which we present 100 people who give back and make Britain a happier, more well-adjusted place. The sixth one is published next month, and we are combing the country for the most inspiring volunteers, charity founders, teachers, conservers of our heritage or wildlife – anyone whose motive is human happiness, rather than feathering their own nest. People like the woman who lost her sight on her wedding day in 1964 and has spent much of the intervening 49 years working and campaigning for the blind; the Londoner who has fostered 850 children over the past 33 years, the 90-year-old who wing-walks for charity, and many more.

But so much more could be done, and this is why I think it high time that we harnessed the experience, time, and energy of the retired and semi-retired in a volunteer force – a Peace Corps, if you like; not for the young, as President John F Kennedy's administration founded it in the 1960s, but for older citizens. It would increase the already good numbers of those putting something back, give many "retirees" a purposeful role in life again, and do much good to those helped. Above all, it would end the wicked waste of millions of our more experienced people.