Unlike cars, houses aren't replaced every 3-10 years. Retrofitting panic rooms will always be expensive - just like retrofitting airbags to a car without them (no one does it).
Similarly, the cost/benefit isn't there to everyone. Every passenger probably has a roughly equal chance of being in an accident, the likelihood that an average person needs a panic room is much lower than the top 0.001% (and probably bottom percentage in the hood would benefit to, but can't afford it, or even giving up the real estate to one, unless it was the primary bedroom).
Airbags were also expensive predominantly because they weren't being installed - and automakers DIDN'T want to install them: https://www.csmonitor.com/1988/0519/abelt.html. I'm not sure cost of production or installation was ever really the significant hurdle to their uptake.