It's a matter of economics. It's a LOT cheaper
to swap the boards in the
field than to troubleshoot them. Just send the boards to DEPO where they are
better equiped (skills and tools) to do component level repair.
I would phrase that, its a lot more PROFITABLE to only do board swaps. Few
customers would be happy paying $150 for a couple caps being replaced, but
when its a "board swap" they never know. It allows the vendor to completely
cover up huge screwups, and makes the user entirely at the mercy of the
vendor. The pendulelum is still swinging though, meaning the consequences
of BS haven't played out, but BS is here forever.