It seems weird because back in the 1990s there were a bunch of companies combining e.g. Canon print engines with their own RIP. But now everything has vertically integrated?
There's near zero money in printer hardware. Ink is what makes money. So few people are printing nowadays that it's effectively a dead-end industry. It's not new, there's very few innovations in printing lately (other than ink tanks but even then, that's not that new). You've been able to print over wifi for a while now and have had access to some sort of cloud printing service for just as long. I could see some hobbyist wanting to develop their own printer but I doubt any manufacturers would sell them a print engine, there's not enough money to even bother replying to an email. Maybe I could see something where you piggyback onto the controller board and run your own software but that's likely such a niche market. Who cares enough to do so? Firewall your printer off and use printers that support generic drivers and can take generic ink (or can be tricked into doing so), you'll save a lot more time than building your own printer that you'll use twice a year.
I'm surprised that HP hasn't shuttered Instant Ink because of the terrible PR they get from people that don't understand how the service works, subscribe for a month for $3, then are all Surprised Pikachu when they cancel the service and they can't use the ink anymore.
