|An early Apple Mac - how do you open the case?|
In the end, though, it was spiky, irritating Apple that got it right and the industry heavies that got it wrong. Because the sealed unit is exactly the way the business has gone. I'm writing this on an (Apple) all-in-one that only allows you to do one thing inside it: add memory. The vast majority of domestic computer hardware these days is either in the form of a laptop, with similarly limited abilities to open it up, or a tablet (or phone) where opening up isn't even an option for the owner.
The change has been driven from two directions. One was the philosophical vision behind the Macintosh, which was computer-as-commodity. No one expects to be able to open up their TV and fiddle around inside it - why should you have that expectation for a computer? It's simply not a very sensible thing to do. The other is the simple fact that we really don't need to open up computers any more. This is partly because so much that you used to have to add in is built in anyway. And also because USB, Firewire, Lightning and the like have provided external connectors that are so fast that if you want to add something you just plug it into a connector. No need to have your sticky fingers straying near delicate integrated circuits and panicking about doing damage with static charges.
So it's not just the mass use of graphical interfaces and high resolution printers that we have to thank Apple for. They realised long before their competitors that most people don't want to be hardware engineers, tinkering around with circuit boards and such. They just want to turn the thing on and use it. (And count me amongst them.)
Strangely, a company began as a hobby business taught the more 'serious' computing manufacturers how to move a product from being something for techies and hobbyists to something for a true mass market.
Image from Wikipedia