I'm a VJ. You absolutely need that many ports when doing visuals at a concert or venue. That was the whole reason I bought a MBP. Now it looks like PC might be a better choice; Apple has abandoned the professional "workhorse" market and is leaning towards the Facebook/email machine market.
First of all, that's Windows only. Says so right there in the listing.
Second of all, it's yet another dongle I have to carry around and potentially lose. There's often not a whole lot of room on stage, so space is precious.
Thirdly, those dongles that convert video are usually slow garbage. If I am performing as a VJ, I need the video to be frame-synced and perfectly synced to the music without lag. I can do that just fine on my current MBP (run 3 monitors at once from the ports built-in to the computer. That's specifically why I bought it.) And now I can do that just fine from some Asus laptop since Apple doesn't seem to want my business anymore.