Continuous ink systems were originally developed for large format inkjet printers. Due to the amount of printing, and the amount of ink used in this type of printing, an alternative needs to develop to smaller inkjet cartridges.
Some large format printers were supplied with large bags such as cartridges containing 100–200 ml of ink. These printers are for household use and the option was not yet available to small business users. You can also buy continuous inkjet system via online sources.
Another development was where the ink was transported to the printhead by a series of tubes. This was often the case where piezo-style printheads were used in professional, large format printers. In this case, the bulk ink was added to a reservoir and the ink was drawn by the capillary to the printhead.
With better continuous ink systems, the process was cleaner and painless (compared to refilling your own cartridges) and allowed printing to continue around the clock. By looking at the ink levels in the ink bottles, additional ink was added, removing only the ink bottle lid, upwards, and then re-securing the lid.
The limiting factor now became the duty cycle of printers. The duty cycle was the number of pages per month a printer was designed to handle.
Funnily enough, it was the printers that became consumables where they would be spoiled by continuous printing and so once they started having problems, the printer was cheaper to replace than it was to repair.
At the same time, inkjet printer manufacturers were aware of the development and appeared to be taking steps to bring more profits back to their bottom lines.