Module-level repair, as opposed to component-level repair, has been a "thing" since the early days of color TVs. When things get above a very-minimal level of complexity, it simply isn't in anyone's best interest to have a random-skill-level technician spend hours and hours finding an IC with one bad gate or Op-Amp section, or an invisibly-cracked resistor. It just isn't.
Does this sometimes, even often, result in replacing a $400 logic board when the real problem is a bad solder connection underneath a 240-pad BGA IC, or a cracked PCB trace (on an inner-layer!) that could be fixed with a jumper-wire? Sure. But the alternative is $400 of labor costs (all-too-easy to accrue at today's $75-99/hr electronic repair-bench rates).
Or have a cracked PCB trace that is intermittent and only fails when the device is very warm so you end up replacing a component that's consistent with the symptoms thinking you've fixed it only for the customer to return when the device gets warm enough to fail again. And then you're on the hook for the rest of the labor and parts needed to actually fix the issue because the customer already paid you to fix it.
Or replace a component that has a history of failing fairly often only to find out it's really a weird power supply issue and you just smoked a brand new part that you can't charge the customer for because you're going to have to replace it twice.
Don't think someone can spend 8 hours troubleshooting something? And then not even find the problem?
I worked in TV repair in the late '70s and early '80s. Sometimes (thankfully not very often) you end up giving the customer a refund on the repair and just telling them you can't fix it.