From an engineering point of view, it's much cheaper to calculate to when 0.01% of cartridges will have run out of ink based on print history vs accurately measuring ink inside the cartridge.

Of course that means that 99.99% of cartridges will be discarded with remaining ink, some of them with a rather significant quantity of ink. And it gives the opportunity to tune this number so cartridges are bought earlier. Although it's up to the manufacturer just how much ink is included, so the usefulness of this tactic is somewhat limited.

I remember what is was like when you'd print a 50 page document only to discover around page 24 you'd start seeing white streaks...and more streaks, and by page 50 you'd have nearly blank pages. Having the printer stop and let you put in a new cartridge when ink is low is a helpful feature.

However, the lockout of third party or even refilled cartridges is just egregious.