Here Andrew explains WHY you need to learn this technique, and it's simple, club gear probably doesn't have beat sync. So if you can't do this manually, you're screwed.
No only that, but when songs are analysed by the software, it can and does get it wrong, especially on older 70's 80's 90's songs. 00's and 10's were mastered using computers and have dead accurate BPM's, older music doesn't. That said, if there's a tempo change in a song, again, the computer gets it wrong.
So if you don't learn how to do it... you may as well go home.
