There are no breakaway, crush zones, etc...in suspension parts. There are no parts designed to separate from the vehicle in a collision. There are no benefits to having such things. Manufacturers don't want a chunk of metal, a wheel/tire, a window, etc. flying through the air addressed "to whom it may concern."
You're right about the loss of stability and braking should the car keep moving/stay on the roadway. That does happen, but in my experience, it's the exception and not the rule.
You have seen pics/videos of controlled testing front on corner crash/collisions, that shoves the attached wheel into the the drivers footwell? What has changed dramatically over decades, IMO, is the crash testing, the more robust safety crash ratings, and insurance companies paying attention to those ratings. Correct me if I am wrong. A wheel separation is not entering the wheel well, and currently has as I know, no downside in the final crash score the vehicle receives. If the shanninhagn's VW played years n eeking out extra mileage numbers with their diesels is not enough of an indicator what companies will stump to, for billions of dollars, I don't think they would hesitate one bit if they know there was a rating benefit to increase a crash score, intentionally or not.
