It's complacency and having consciously or naively relied on security through obscurity for so long. Now that LLMs are a thing, such design flaws are trivial to expose even for the lay person, leading to a pretty massive awakening of how bad it all really was all this time, or what kind of stupid decisions have been made (i.e. the supermarket cooling incident).

I suspect the problem will solve itself though eventually, as the threat level of bad security practices has risen now, so companies have incentive to throw money at the problem for risk management, and LLMs may just as well assist with detecting potential exploits during the design phase. Thinking of it this way, I believe that security will actually improve a lot in the near future.