Even then we still do field work because there are a lot of people who would rather have someone else do it to be safe/convenient. Makes sense in some regard as when a tech does it, you get a warranty and any mistakes or accidents they make should be covered by them.
I can agree with that. But I would say that the option should be there and if whatever company wants to say that any repairs that they have to make repairing the owner's blundering is on the owner.
Now, when the device is out of warranty, I think that there should be no limitations for the consumer, there used to not be. Schematics used to come with purchases (on most things, maybe not on everything, when this was the thing I wasn't dealing with large format printers, so maybe they never did), now they don't. It seems like in so many ways we are going backwards. But whatever, "you" do "you" (this is the general "you", not any one specific), but don't expect much sympathy when things don't go "your" way. Just do what the vendor wants and upgrade to get the warranty and toss out the otherwise perfectly good piece of hardware (I'm surprised that the tree huggers aren't all over this, regardless if they believe in right to repair in of itself).