>There is, quite simply, NO good argument in favor of non-maintainable equipment, unless your goal is to increase profits.
As a universal assertion, particularly in the realm of products intended for personal mobile use by the general population, this absolutely and utterly wrong. The fundamental core issue is that many forms of maintainability require dead matter, simple as that. Take removable vs non-removable batteries, perhaps the most classic example in portable electronics: having a removable battery requires user safe contacts that can handle repeated mechanical strain, the battery itself to have its own protective case, the device case to have a way to interface the battery and the resulting structural support and tradeoffs therein, the dimensions and shape of the battery are significantly constrained, etc. All of this boils down to significant additional stuff that isn't battery, or performing any other useful role for that matter, but rather is simply scaffolding/support infrastructure. In other words, dead matter. There is no free lunch. A removable battery fundamentally can never match the size/weight/performance matrix of a non-removable one, full stop. That's the tradeoff for being able to swap it. In this specific example there are additional potential tradeoffs too for some use-cases (it's significantly easier to have a higher degree of harsh environmental tolerance with a fully sealed system for instance).
Now, yes, there is absolutely room for reasonable disagreement about what side of the tradeoff is correct for any given application or use-case. There are times where the utility of maintainability or modularity is well worth a reduction in default performance. But there are also many cases where a higher percentage of active matter in a product is a legitimate feature to the majority of its intended users. The "No True Scotsman" fallacy you use to start your argument should have been a flag and caused you to rethink the rest of it.