Near the beginning of my career, I talked to a greybeard who harrumphed at me discussing something-or-other and said "computer security is an oxymoron". I thought he was being too pessimistic, nowadays I realize he was right.
It also requires actually caring about security and putting effort into it. These data breaches are usually systems where little attention was paid to security in the first place, and e.g. getting ahold of one user's password is enough to lose the game. Getting companies to care about security is really hard, but it does happen.
That's overhead that businesses really hate paying as it's diverts software devs away from making new features.
Who do you think employs the top-level criminals?
outside of english class "secure" is relative and context-dependent, not binary.
My point was that computers are as secure as human(s) who programmed them were careful and competent. Computer security is ultimately human knowledge and reasoning competence (plus time/money tradeoffs, if made willingly)