Why does today's music have no lifespan, like the 70's 80's some 90's?

When you hear a track from the 80's it gets you up on the dance-floor
so fast.
same as 70's dance hits.
YET why does music from the last 15 years have no nostalgic feel to
it, almost like the song appears for 2 days then disappears never to
be heard again, music has become so throw away.
why do we need to go so far back to feel good.-by the way no im not
old unless you think 35 is old, that's pretty sad.