Full disclosure, I am a former HP Engineer who worked with HP Labs, mostly in the Computer Vision area, and 100% productizing their labs research into viable profit streams. Your milage on my comments may vary. I am not going to attempt to justify what HP does but it will probably sound as though I am (try to remember myself and my entire team were laid off as unprofitable because we were 5% off on our $1 Billion revenue goal, that stung a bit). I will attempt to throw a few business comments that no one is mentioning, and a few engineering thoughts that no one is sharing, into the mix so that you can see an entire picture.
How much would it change your perception if you found out that a good portion of the refill ink market is also supplied by HP? Internally, we used to call HP an Ink seller thinly veiled as a technical company. They make more money in the refill market than they do in the cartridge market, though their gross in the cartridge market is still very high. This is because selling bottles of ink with syringes and instructions to refill is way cheaper than selling new cartridges with the manufacturing of the rather complex pieces in the cartridge, the packaging, the shipping to the stores, and the marketing. So why would they suddenly shoot themselves in the foot and kill that market? I'll get there.
I hear you say "HP makes so much in ink sales they are trying to monopolize the market and squeeze just a bit more revenue out of it!". I hate to break it to you, most people just buy the refills at Walmart or Costco from the giant displays and have no idea that their printers will be borked if they don't. A majority of the refillers refill with an HP authorized refiller (those people you meet in mall kiosks, most are authorized, they won't bork your printer). Actually HP loses far more money from people using crappy ink refills and crappy knock off cartridges and then calling up to customer service and saying their printers were ruined, thus sending out new printers and ink. The cost of the customer service to deal with that alone is so massive for HP it makes one of the main budget line items at all of the board meetings.
So, the technical. Someone in the comments mentions "Why not just build a new printer company! Printing technology can't be that hard!" A further comment says "Oh you could, but wait until the patent lawyers come to get you!" Well, true. A lot of printing technology is patented and pretty locked down. But it's disingenuous to say that printing technology can't be that hard. Imagine the following scenario:
You just bought a brand new iPhone 7 with a 12 MP ultra clear lens. You have a party at your house and snap a photo of your child with their technically inept grandparent. Grandparent says "I don't use the facebooks, and I don't understand mail with an e, print me a copy of that photo!" No problem, your HP printer is wirelessly on your network. You print from your phone onto photo paper.
Where's the hard part of this technical equation? Well a ton of engineering went into that small 12 MP camera, processing, the wireless network for delivery, etc. But hell, you want to be able to print that photo on any old glossy paper you bought from someone, using a knock off cartridge, with any ink they shove into it. And it better come out looking like an Ansel Adams original, or damn it, HP screwed you as a consumer again!
In order for you to get the sharp colors in the right hues with the perfect lines it takes a lot of engineering. In order for you to get the paper to come out dry (either we're talking photo printing or just your black and white document) and not bleed onto the back of the next page in the tray, it takes technology. I'm sorry Cory, but your analogy with the toaster does not hold true. If I get a new toaster and throw bread into it, I only have to try a few dials and settings to get my toast to come out the way I like it. With printing and ink, there are literally thousands of variables from head design to spray to the viscosity of the ink, and on and on and on. Remember for a moment, consumers don't want think about the angle, velocity, and aeration of their red ink, not to mention how to combat humidity to not ruin the viscosity of the ink between the head and the paper (even if it's only for a fraction of a millisecond). They just want a perfect print. And HP just wants their consumers, on the whole, to like their products and not complain to much, and keep on buying stuff.
Now, if you really want to scare the pants off of HP and get them out of this market, digitize everything and stop printing. Get tablets for everyone you know. Use them at work and at home. Print less. This is what really worries them in the market.