OP was wondering, dunno if it's been brought up by now (it likely has since it's been a few days), but reasons for DDOS can be as simple as "it's there".

Think of the most angry, cantankerous Internet troll you've ever come across. Now, with all their pointless spite, give them a tool they can use to massively inconvenience people everywhere. Now, introduce a giant target like online game servers that huge amounts of people congregate their traffic at. It's just a matter of time.

That's reason enough. It's sometimes no deeper than that, and that's just the reality of the internet we have.

Security is always the opposite of convenience, and striking a balance is what we have to do.

I'm not saying anyone's wrong in complaining about this, by the way. But, our inconvenience is often the only trolls are after.