Why? DRM certainly doesn't prevent piracy, and from at least anecdotal evidence removing DRM reduces piracy and increases sales. There are a few studies that I found that bear out the last point, but I haven't read them fully and am unsure how correct they are.
IMHO, DRM causes there to be a delay (provided the game is not leaked) between game launch and game available for free on the internet. When your target audience is known to be... impatient... that might make a lot of difference. Unfortunately it comes down to not being able to trust your own audience, as the author said. I would prefer DRM free everything as well, but if the economics support it, it would be pretty silly to ignore that.
That's anecdotal evidence too. There's nothing to show that it being DRM free caused it to be pirated more. I've seen figures that suggest that 90% of installs of a game come from pirates, so at 85% (18,000 legitimate installs from 120,000) anecdotally they seem to have reduced the level of piracy. The effect on their servers sounds like poor infrastructure design more than anything else, especially given they were able to deploy an infrastructure fix fairly rapidly.
My point was it's unclear that the economics does support it, and the evidence that's slowly accumulating suggests that in fact the economics supports the opposite.
They had server infrastructure for an estimated 50,000 players. 18,000 players bought the game and were trying to play. Over 5x that number in pirates logged in, and because they didn't use any multiplayer authentication (accounts or some such), they had to support them like paying customers. In other words, going DRM free caused an overload on their server. It sounds like an underestimation of the amount of pirates they would get more than anything - they had over 250% capacity for paying customers.
Also, only Ubisoft claims piracy rates over 90% as far as I can tell.
World of Goo (90%), Machinarium(90%-95%) and the PC Gaming Alliance (90% for high end titles) have all claimed piracy rates of 90% or above.
Also there seems to be a gap in your reasoning, going DRM free didn't cause the overload on their server, unless you're claiming that going DRM free caused people to pirate it. The huge pile of (previously) DRMed media currently being pirated would beg to differ with you. They did use accounts (or a code per game), so the pirates were unable to log in to the server, but the fact that they were trying to is what was causing the problems (from the update at the end of the article). If they'd had DRM, it would have been cracked, people would have pirated the game, tried to contact the servers and they still would have fallen over.
If they had implemented DRM for multiplayer access to the server, they would not have failed. Attempting to contact a server and being told 'No' isn't the same as having a connected player. I'm talking Steamworks-style DRM here, which is online logon for multiplayer, requiring authentication against the server and username / password tied to purchase. It works well for that purpose.
If they had used it, those early reviews would not have suffered, and their servers would not have been overloaded short of a DDoS.
Because "EMOTIONS!" People aren't necessarily rational when it comes to their emotions because emotions aren't necessarily rational.
It's also pretty hard to get over your fear about your life's work being wasted especially when it's a big sacrifice for you. Read the article, writing a book makes this guy die on the inside a huge amount. If he doesn't get paid halfway decent, the sacrifice definitely isn't worth it. And since we're in emotional thought realm, no DRM = priacy = people not paying for my book = these fuckers are mooching off of my hard work = why am I doing this to myself? = can't go there, ergo can't have piracy.
Why? DRM certainly doesn't prevent piracy, and from at least anecdotal evidence removing DRM reduces piracy and increases sales. There are a few studies that I found that bear out the last point, but I haven't read them fully and am unsure how correct they are.