This is 18 months old but might help explain it.
The market is driven by wiz bang state of the art and beyond products with product cycles short enough so a segment of the consumer base renews their phones sooner than they encounter problems and the associated new product hype carries them along. Leave one manufacturer and what are your choices, just others who seem to treat their customers in a similar fashion although perhaps to different degrees.
Although Android is Android, the different bloatware and value added tweaks make moving from one to another a learning experience that can be minimal to irritating. I went from a Samsung (big bloat & tweaks) to a Moto (no bloat | tweaks) and it took quite a few weeks to get comfortable again. My next will probably be an Oppo, different again with their Android base ColorOS.
Manufacturers know this, they are not interested in setting precedents by what they see is unwarranted cost of supporting their customers, but as you ably demonstrated a loud enough complaint can get results, and good on you for persevering.
Most sales are because of products and features, and as with other products and services even those with the worst reputation for 'customer care' do not seem to suffer degraded P/L because of it.
Unfortunately Samsung is not alone in that regard!