We can only blame the manufacturers for that one. There again that was obviously a business decision of the many as it kept a cost factor to almost non existent, their prices competitive and gave built in obsolescence to ensure demand for new cars continued apace. They, no doubt, never thought our Omega's would still be on the road almost two decades later!
did you have a liquid lunch ?
Cars are made of steel sheet welded together. Most of the resulting structue gets coated when it's dipped. Then the bits that can be reached are painted. The car spends its life outside in the weather with very little attention.
Put all that together, and it's not going to last forever. Look around and count just how few cars make it past 25 years.
Omegas are better than most cars of their contemporaries - the body is from the seventies, so that's Granadas, 5 series, CXs, Renault 30, MB200 etc which are all notorious rotboxes.
No!
What I mean is that if adequate anti-rust treatment, rust guard, or whatever it is called, had been applied when new, the rot would never be so great.
As for the cars back in the 1960's and 70's no anti- rust treatment was applied, and thus motorists who cared for their new vehicles had the chassis coated in an anti-rust treatment / Guard, who's name escapes me. The majority of cars never had this, so of course my old A40 rust bucket, let alone cars like the Viva's, and many more started to have very large rust holes appearing all over them.
Now, due to consumer pressure, cars started to be built with some form of treatment and the rust problem on not so old cars improved greatly. If the manufactures cared about it, I am sure it is not beyond the wit of man to fully coat the metal with modern anti-rust treatments so that it did not rot even after 20 years. Yes, of course metal gets rusty. But man has answers to that but it is still not commercially viable to do all they can to prevent rust. Just like the ever lasting light bulb, no manufacturer is going to produce it if they want future sales!