Happy to be corrected on this and I'm sure those who work in advertising will but doesn't the age of the music reflect the demographic that the advertiser is aiming at?
Generally ads using 70s music are aimed at those in their 60s/70s - those with the most disposable income.
Similarly music from later years are trying to appeal to younger buyers.
This is why we rarely hear Cliff and other rock'n'rollers on ads and we are seeing fewer of those godawful contrived dancing scenes on TV ads.
Isn't this the case??