Here is the way I see it,
A laptop DJ comes to a gig and has 2k-10k tracks.
A CD/LP DJ comes to a gig and has 100 tracks in CD or LP form.
How is this laptop DJ going to fit his 2k-10k tracks into one two hour set?
I often hear the laptop DJ brag about how many tracks he has on his computer, I personally let my CD wallet do the talking for me whilst I check out tits and ass on the dancefloor ;).
To each their own though. There have been gigs where I have Scratch Live or Traktor readily installed on my laptop and will come in, plug in, play simply because there are only controllers available to play on.