Because now you don't need talent to be a success. You need promotion and image.
One Direction aren't any different to any other boyband, ever. And that does include the Beatles. When they tried to crack America they went out with the lovey dovey pop songs to appeal to screaming girls, get fans, exposure, and therefore sales. Then the Beatles used the fame to release better songs, like they had been doing in the UK, and it is unlikely although not impossible that One Direction will ever do this part. Take That started as a teenie bop group for girls and when their fanbase got older they went solo, some of them made better songs that appeal to more than just screaming teenage girls. It's just what boybands do. NSync with Justin Timberlake making decent pop songs after using the band is another example.
When One Direction sing 'that's what makes YOU beautiful' every average girl with low self esteem thinks it is about them. When the Beatles sung 'When I say that something, I wanna hold your hand' every average girl...etc. She Loves You. Love Me Do. Same deal.
Record label tactics, here's some songs, now sing them you dumb kids, and look pretty doing it. No indication of talent in the comparison, just promotional skills to sell. Obviously the Beatles, the Who and the Stones have something more to them than just jumping around flicking their hair and singing stupid songs. But at the time they needed to, and their longevity shows this. When One Direction are replaced by some other product, people will forget all about them. Sadly the replacement group will become popular and we can all hate them instead.
I doubt kids ever actually think for themselves. Fads, group mentality, popularity and being part of the crowd at school is such a big part of growing up.