the only explanation possible is that using Lighting is profitable for them
I gave you another possible explanation in the comment you replied to. They have a whole product line to move and the left iPhone for last, because it has the most impact, and if they leave it for last, it will have less consumer impact. Why not assume good intentions when there is a reasonable explanation?
If it was all about the money, why would they have used the Qi standard for their wireless charging? Why would they have gone all in on USB-C on MacBooks, facing a ton of backlash, to push that port when everyone else was hedging by just including 1 USB-C port at best? Sure they make money from Lightning, but it’s likely a rounding error on their bottom line.
It’s also not a bad thing to have some cable certifications. I’ve seen tear downs of cheap 3rd party charging bricks, or tests of cheap cables, and they’re all really bad and out of spec. They’re cheap for a reason. Maybe that will lead to device damage, maybe it won’t, but I’d rather not risk a $700 phone over saving $10 on a non-certified cable/charger that cuts corners. It happened to my sister, I went against my judgement and bought her a 3rd party cable she asked for instead of the Apple one I thought she should get. A few months later she called me crying because he phone wouldn’t charge anymore. I felt like shit, even though I technically just got her what she wanted.