They gave their reasons for the conference today:Alx said:And even if it wouldn't have changed much, I think that they could have made the press conference a week earlier, since they didn't present anything today that they didn't know then.
http://www.4gamer.net/games/036/G003636/20110501003/Q.4月27日に事実関係は分かったはずで,なぜその段階で会見しなかったのか?
A.(平井氏)実際問題として4月27日の段階で発表した「漏洩の可能性のある情報」は,その時点で判明していたもの。ただ,会見にあたっては「再開に向けてどういうスケジュールか」「再開にあたってどうサービスを展開するのか」「個人情報保護に向けてソニーがどう動くのか」といった点について情報をまとめつつ,保険会社などとも協議するなどして,最短のタイミングになったのが本日。
In short: the delay was not for how much they knew about the hacking, but because they were still deciding and coordinating the actions and measures that were going to be taken in response to the incident.