The use of old songs to create dance music

Old songs and music, mainly from 70's and 80's, has become essential for current dj's.
The trend seems to be clear: dj's are using songs from these eras to create the latest electronic anthems of the night.
But this tendency started around 10 years ago or even in the mid 90's when popular dj's from the dance scene began to used sounds and make covers inspired in old former number ones.
Songs from the BeeGees like You should be dancing and Stayin' alive became a new inspiration for the new songs by N-trance and Blockbuster.
During the 90's Dj's like Armand Van Helden, Phats and Small, Yomanda, Bamboo and Stretch n Vern used 70's songs and typical sounds -melodies- from this era to create such songs as You don't know me, Turn Around and I'm alive.
By the beginning of 2000 and to date, the trend has kept growing very much that almost every dance tune has that influence of the music from the 70's and 80's.
Indeed, this massive influence, helped some dj's to reach the top spot of the national UK charts...Call on me by Eric Prydz, Lola's theme by The Shapeshifters, Out of Touch by Uniting Nations and some others became the most played songs for weeks. Also, they became the anthems of the clubs.
Even though, every song has a new vibe they still keep this influence from old sounds, either from the disco scene or the post-disco scene.
It is important to mention that sometimes the Dj just decide to use part of a song or the basic melody of it, meanwhile some others decided to make a full cover of the song and release a new version.
No matter what the case is, old songs and rhythm have become a massive influence for current dj's.

Take a look at some of the best new songs inspired by the oldies...

1) Eric Prydz - Call on me (cover of the song 'Valerie' by Steve Winwood's released in 1982)
http://www.youtube.com/watch?v=L_fCqg92qks

2) N-trance - Stayin' alive by (cover of the song "Staying alive" by The BeeGees released in the 70's)
http://www.youtube.com/watch?v=qiKOif0UKRM

3) Yomanda - Synth & Strings (inspired in the song 'Dance yourself dizzy by Liquid Gold, released in 1979)
http://www.youtube.com/watch?v=YbLpibHT5zY

4) York - On the beach (OTB) (inspired by the song 'On the beach' by Chris Rea, released in 1986)
http://www.youtube.com/watch?v=FF9P5xcCzb4

5) Stretch n Vern - Im alive (inspired in the song 'Boogie Wonderland' by Earth, wind and fire, released in 1979)
http://www.youtube.com/watch?v=iNsbC5hopR8&feature=related