Sir you are a materials engineer of course, BUT, I find it highly unlikely that you have ever studied the consequences of a high speed impact.
The cars you have put forward as instances are for sure stronger bodied than the new ones. But the scenario in which YOU consider them strong is, how should I word it, useless?
What you're saying is that if a civic 95 crashes/bangs into a city 2013/civic 2013, the latter one will probably crumple to death while the civic 1995 MIGHTY MUSCULAR will survive the crash with probably a bent fender or a broken bumper. Am I right?
From a certain POV, it looks a monetary benefit to me.
Sir let me tell you that modern cars are designed to perfection for distributing almost every little and enormous force generated as a result of a high speed crash. In the past, people used to be killed by the forces alone, the bodies didn't crush them inside.
The results of a TAYT MAZBOOT MUGHAL STEEL body are for example, in case of a head on collision, the engine will rip apart the firewall area and turn the passengers into dead meat. Trust me I have seen many impacts like this.
However in case of such impact in a modern car, its chassis will crumple, so will the engine and several components of the engine bay to help the passenger cabin stay intact.
I repeat again that these are compact sedans desgined to withstand impacts at normal speeds. If you swap a bloody all motor in them and start track racing, I am sorry you WILL DIE. No company claims impacts at such speeds.
Ever seen a mercedes CLS 550 crashed? I bet NO. For your eyes only, call this a teen dabba https://www.pakwheels.com/forums/spotted-crashed-wheels/206301-wrecked-cls-550-a
Bhai jaan you don't seem to believe almost 10 people over here who are using this car in their daily lives rather you are producing Internet results and trying t falsify practical examples with them. This is wrong.
WHAT IF I post here a honda city idsi 2007's example which did 19KPL with a trunk full of luggage and 4 persons on board? To add to it, the drive included a steep climb as well. 
Phir kya kahen gy aap bhai? 
What we're saying is a result of 217+3=220 thousand and 60+20=80 thousand kilometers driving experience respectively. Isn't that a bit too much for a practical thing?
Saadi bro's car even has CNG in it. Come on sir, share your own experience if you have ever driven and kept a honda city for daily use.
Allah maaf kre sir, Allah kre aap kabhi bhi kisi puraani tight car main real accident main involve na hon. Otherwise you won't be saying all this.
And WHAT? Are you effing kidding me bhai? Do you even know what you just said? PKDM bodies aren't crash test approved? HAHAHAHA thanks a million for the GREAT GRAND LAUGH of 2013.