Before the year 2000, it was common to say only the second part of the number,with the article, for instance: il 98, l'84 and so on. We were also used to say gli anni '80 (meaning 80s), gli anni '30, and so on. Then we lost this habit. It would have been weird to say l'uno il due eccetera :) On the other hand to say duemilaeuno, duemilaedue (yes we used the conjunction "e" till 2009) was not that long to pronounce :)
Anyway I think that sooner or later (2020? 2030?) we will come back to the habit to shortening the years: be prepared :)
ciao!