This stuff becomes important when you have an item that is expensive enough to bother repairing.
I guess most people would be pissed if they spent $20,000 on a new car and when the clutch failed were told they needed to replace the entire car or spend many thousands of $ having the entire transmission rebuilt rather than being able to take it down to the local repair shop and have them do it within a day for a few hundred $.
"I guess most people would be pissed they spent $20,000 on a new car and were unable to easily service it themselves".
And my answer to that is no, most people wouldn't be pissed. They would take it into a repair shop that can handle it.
If the car has been designed in such a way that a relatively common maintenance task (changing spark plugs, upgrading RAM or whatever) is now much more difficult (thus expensive because the mechanic will charge you for more hours of labour) than it otherwise would have been (or impossible) and reduces your choices of service providers then this is definitely not a good thing to the customer.
Of course sometimes such design changes are inevitable trade-offs against something else. For example a laptop is less maintainable than a desktop but you gain vastly increased portability. In this case (the iMac) it's not obvious what the gain to the customer is.