When we started in advertising in the late 1980s, the 'Grey Consumer' was a hot topic. The proportion of older people in the population had begun to rise, and many were surprisingly affluent. These trends were forecast to accelerate as the Baby Boomers turned into 'Empty Nesters'. Soon we would all be chasing the 'Grey Pound'.

But fast-forward 35 years, and we seem more obsessed with youth and Millennials than ever. Those demographic forecasters weren't wrong. The proportion of young people has indeed fallen and the proportion of older people has increased in most developed markets: in the UK, the over-45s outnumber 16-24-year-olds by 4 to 1.

These over-45s are more affluent too – accounting for some 50% of consumer spending and an even larger share of wealth, with these proportions climbing steadily, even throughout the recession. Young people, however, are having a tougher time. Debt, soaring housing costs and high unemployment mean young people in developed economies have less money to spend nowadays – and the recession hit them particularly hard.

So, as the experts predicted, the real money now increasingly lies with older people. Why then are we still obsessed with youth?

First, get 'em young, the logic goes, and you keep them for life. This is true for some categories, such as bank accounts, where switching is still quite rare. But in most categories, brand switching is too frequent to justify such a long-term approach. Even car-makers find it hard to justify focusing on younger drivers, despite high sales values and long purchase cycles.

The second argument we frequently hear for focusing on Millennials is their difference. They consume different media, live different lives, and have different brand relationships. Conventional advertising won't cut it here, supposedly. However, this can be exaggerated. While they may, for example, spend less time with TV and radio than older people, traditional channels still account for over half of their media day.

Third, it's argued that Millennials represent the future. What they do now, everyone will be doing one day. This is probably the weakest argument of all. Our job is to sell to society as it is now, not as it will be in ten years' time. Young people change their behaviour as they grow older, so they're not always a reliable guide to the future. We need to distinguish 'life-stage effects' from 'cohort effects'. Because young people watch less TV than average, TV viewing is not necessarily bound to decline in the future. Young people have always watched less TV than older viewers, because they go out a lot more.

We suspect that advertising's obsession with youth is partly due to lack of perspective. We all have a tendency to assume that the average consumer is someone like ourselves, and people who work in advertising are mostly quite young. Now that they do less TGI analysis and fewer focus groups, young planners are often disbelieving of how old the people buying their brands actually are. (TGI reveals, for example, that the average new car buyer in the UK is over 50.)

But maybe there's something else. We all admire the energy and creativity of youth. Youth is sexy, fun, interesting. Ageing, however, is embarrassing, unattractive and a bit scary. So perhaps the real reason we ignore demographic realities is that they remind too many of us of our own mortality. This could explain the phenomenon we've noticed whereby the people who bang on most about Millennial are aged way past 30.

Perhaps Millennial themselves, far enough from mortality to fear it less, could lead the way in intelligently addressing the needs of the people who really have the money nowadays. But please avoid names including 'grey' or 'silver'!