The only thing wrong with a soldered wire is that if you ever have the wire get HOT, like a short circuit, or an over loaded circuit, it can melt the solder and come apart. That's the reason you don't solder wires in a house installation. An overloaded circuit makes heat. .
I'm sorry, but I have to argue your point here.
I think the fact that solder isn't used in residential or commercial wiring has WAY more to due with practicality and feasibility than anything else.
You are commonly joining multiple 14ga, 12ga, or larger solid copper wires. Which is fine, but that would take a substantial iron in many cases.
Then you have to do so at dozens, or more likely hundreds, of locations throughout even a modest house. Many of which are up on ceilings, high on walls, etc. You would need a big, battery powered (portable) or butane powered iron, and it would just be miserable work. Sweating pipe with a torch is similarly miserable, but at least the torch is portable and has the BTUs needed.
MOST of the cases of residential wiring I've seen overheating due to overload were simply because somebody replaced a fuse or breaker with one that was not sized appropriately to the conductors.
The majority of cases I've seen of residential electrical fires and near-fires were due to poor connections. Namely, the push-in terminals on many residential switches and outlets. If it were up to me, they would be outlawed. The little "blade" inside the terminal wears into the much softer copper wire over time, and in 5-10 years you have a bad connection that is heating, arcing, and sparking.
A good solder joint at the device would eliminate the majority of electrical faults in residential wiring. But it's not practical.
Edit: After reviewing the NEC, it seems that most of their concern is due to mechanical failure of the joint. Not from heating, but simple mechanical pullout.
I imagine that's in there for a reason. I would bet that at one time solder was used and it was not used correctly so they just outright banned it.