Fair enough for you and your needs Diki, but I think you're misunderstanding me re looping/synching etc. More to the point, I'll guess I'll speak for myself rather than Donny at this point:
I want the flexibility to say, start a well known song (be it old or new) with a loop either sampled by myself, or an Off-the-shelf-Factory beat, so that the song I'm playing sets a certain Tempo/Vibe on the Dancefloor. (Btw, that song might well be an older slower song from another Genre that works well with an upbeat dance groove.)
THEN
I want to be able to segue into another song - in whatever way I want.
For example we're currently doing "TIK TOK" by Kesha, and whilst we're playing the song, we add in vocals and (some) samples of Madonna's Holiday, along with my live playing of whatever sound I choose. This is essentially doing a "mash up" of two songs - this generation's version of a Medley, if you will, (albeit a 2 song Medley - sometimes we can work in a 3rd song depending upon timing and chord structure) and I want to be able to crossfade to, or simply add/bring in, a style OR Sample OR MP3 OR SMF all within that "master beat" within that song-within-a-song.
That DJ Style Dance Remix and/or Mashup is simply another tool to entertain people and keep them dancing instead of merely doing the standard "Radio Edit" of a song.
It's another way of doing your own version of a song, which I'm sure you yourself would often do Diki (a big band swing arrangement of a more sombre song for example, or a Classic Foxtrot Jazz Standard done in a Rhumba style etc etc etc).
The Dance Remix/Mashup is just another way of expressing yourself musically in an updated way, and because it (usually) involves much pre-thought in how to put the songs together, using a number of different elements (Style/Loop/Played Live Samples/Piano or Organ and/or Bass parts played live over a loop even) it requires a lot more than merely "DJ-ing" would normally do.
(No offence to any DJs reading!!
)