"We want to use a complex mechanical product. But we don't care about the spec sheets, the design documents, the repair manual, the component blueprints and sizings and moulds. We just want the machine to work! We'll pay someone to reinvent all the components if we ever need to change it."
It's a stupid and short-sighted policy.
NASA probably kept every piece of paper associated with their missions while they were still operational. That way they could refer to 30-year-old assembly listings and fix bugs. The Apollo computer code went through revisions for every single mission.
Not wanting to do this, but to just push out products with no way to repair them is fine. You can do that. Apple make a living doing that.
But basing your long-term infrastructure that's going to be in place for 30 years, upgrading your existing one that's so critical it can't go off so you have to emulate the old system, etc. on such a system is stupendously idiotic.
You want the blueprints. Even if those blueprints were made for you by the machine manufacturer. Then you can get other people to make compatible parts. You can change things as necessary and see original design decisions and their causes. And you have everything you need to continue after the original company goes bust.
Computers used to come with circuit diagrams. They used to come with repair manuals. They used to come with component listings. You can still maintain those things on the basis of those documents. Whereas last-year's-iPads are in the bin already as they can't go to iOS 10, or whatever.
Your software should be no different. If it's business-critical, and especially if it's bespoke and highly customised, why would you NOT want to have all the plans and sources available to yourself? All you're doing is giving yourself a dependency on a company that has a method to screw you over for money every year until they go bankrupt. And they can choose the level of their screwing over depending on their own circumstances, not yours. Oracle are famous for this. Microsoft are no different in the long-run.
What we really need to wake people up is a collapse. Literally someone like MS going under and not selling something recognisably Windows or Office any more. Or completely hedging on cloud and stuffing everyone up who has masses of internal, hand-made, customised back office setups. It's unlikely, but that's the only time people might look at their systems and think "Oh. That's now gone. What do we do now to continue running day-to-day? And how can I stop that ever happening again?".