The reason being people in my country don't really care about warranty, would go out and buy a cheap cartridge-based printer, then bring that printer to some hack shops that will "convert" that printer into a tank-based one, allowing you to use any third-party ink.
So manufacturers keep absorbing loss on their lower-than-cost printers and couldn't make a profit from ink sales.
That's why cartridge-based printers are slowly being phased out for ink tank printers... So manufacturers can grab profit directly from printer sales :-)
But they’re not the ones cranking out the $20-$50 inkjets that litter the shelves at Walmart/Best Buy
But most of the time, it's fine, and the ink is cheap.
It costs HP/Canon at least (if not more than) $49 to build a $49 inkjet all-in-one.
Consumers mostly tend to make their purchase decisions on the margin, and so the razors-and-blades model works well.
I guess there may be a few recent exceptions to this like the Epson Ecotank, although I don’t know how profitable that has been for them.