Because exposure to sunlight produces vitamin D in the body, and deficiency in that vitamin has been linked with the development of diseases like diabetes, breast cancer, prostate cancer and tuberculosis. The newspaper also cited new research suggesting that a lack of vitamin D can play a part in the development of multiple sclerosis.
More than that, said the Observer:
In 2007, the Department of Health revealed that up to one in 100 children born to families from ethnic minorities now suffer from rickets, a condition triggered by lack of vitamin D in which children develop a pronounced bow-legged gait. The disease once blighted lives in Victorian Britain but was eradicated by improved diets. Now it is making a major resurgence, a problem that has been further exacerbated in ethnic communities by women wearing hijabs that cover all of their bodies and block out virtually every beam of vitamin-stimulating sunshine.
A major health campaign, offering dietary advice and vitamin D supplements has since been launched. But for many doctors, it is not enough. The nation's health service needs to re-evaluate completely its approach to vitamin D as a matter of urgency; establish new guidelines for taking supplements; and scrap most of the limits on sunbathing currently proposed by health bodies.
Why did things change so quickly in the 1990s?
It is not as if skin cancer poses such an overwhelming threat that it can wholly explain the change. Back in 2005 Sam Shuster, Emeritus Professor of Dermatology at the University of Newcastle upon Tyne, wrote on Spiked:
To find an explanation for the rise of concern about exposure to the sun, we have to look elsewhere. That rise took place in that odd period between the fall of the Berlin Wall and 9/11. Rather than congratulate themselves in living in a happy age, people looked for something else to worry about - hence the emergence of strange scares like the satanic ritual abuse of children and the millennium bug. Maybe skin cancer was another one of those.
And we cannot ignore the rise of environmental concern - and in particular concern about man-made global warming - in the period. There was a widespread feeling that there was something wrong with the climate, and you heard people say that they "never used to burn like this". Hence people began to worry about exposure to the sun.
But maybe there is a clue in Professor Shuster's article. He writes:
The high incidence of skin cancer in Australia is the product of a high UV exposure in a population whose ancestors included many with pale, freckled skin and red hair. It should not be extrapolated to different populations living in sun-deprived climates.