What regulation are you proposing? Forcing all computers to be locked down so hard that users can't install malware?
edit:
I remember thinking in the 90's that it was weird as hell that the operating system sits in the same folder tree as the users documents, applications live there too! What a concept? Like keeping your socks in the same drawer as your bills and plumbing tools. Spare tire in the kitchen. Lawn mower under the bed.
Would these companies leak their own business critical documents? No. So why can't they be forced to treat sensitive customer's data the same way?
The data was stolen from the users' computers, by malware installed by the users themselves.