This is from July 1995, so the very early songs (eg January) are probably not in the site, also no music videos released after July are there right now.

Also many of the songs in that list are currently on the site, maybe you didn't got lucky (is random) and you didn't get the ones that were played enough times to be memorable (for you)

And no to mention human memory is very bad ;) ... (only half joking: http://science.time.com/2013/11/19/remember-that-no-you-dont...).