Well, in this case its just that Arcen believes in no-DRM. That right there is why. But for the sake of argument, well, I guess the downside would be the higher costs associated with the system, I mean, there are costs regardless. Time, money, technical support, etc. It would also get Arcen some bad PR for using DRM. Maybe not a giant amount of bad-PR, but they would get some. And then there is any potential server problems that would crop up due to the DRM.
I think I'm repeating the same thing, but at the end of the day, the general expectation of Indie-developed games is that they do not include DRM period. End of story. I have that same expectation too but I'm anti-DRM regardless of who develops it. So I guess its not so much that its just technical reasons not to do it, but social reasons not to do this particular DRM your talking about. And if you tick off the legitimate buyers, well, that's bad.
King