Now we have dozens of car seats designed by engineers and thoroughly crash-tested to create car seats that get thrown away (or are supposed to be) after any impact event. Makes me feel like we are much richer than we used to be.
I'm in my 40s, and I've been a passenger in one collision that required a tow truck, something like 20 years ago. Most people I've talked to have similar experiences in terms of frequency of serious collisions.
It's less expensive overall to do it this way.
That force and momentum has to go somewhere and it's better to absorb it into the car seat and consider it a consumable than to transmit that force into the child it's meant to protect. The same thing applies for helmets. A motorcycle helmet is a consumable item and should be discarded after a crash as the internal foam structure will be deformed and could fail to properly absorb the impact forces in a subsequent crash.
I’ve disposed of them as the youngest child outgrows them, but they’ve never been in an impact.