Technical Underside Corrosion Protection

[Peter Pick-Up]

Perhaps the whole industry is falling back into its bad old pre-1990 ways

No, no that won't happen, a lot of car manufacturers used recycled, Russian steel in that era, causing all the big rust problems ( Alfa, Fiat Opel/Vauxhall, VW etc. etc.)
Today, the steel quality is much better, but factory rust proofing is almost absent.
So a professional anti-rust treatment is something every modern car owner should consider, even more if he/she wants to keep his/her car for a longer period of time.