The main benefit of using Continuous Inking System is the save cost of the printer. Now that the CIS itself has become very affordable, and buying ink in bulk has never been cheaper, the cost of the equivalent amount of ink in a cartridge is now pennies rather than pounds. Even compared to the cheapest compatible cartridges on the market, you are only paying a fraction of the cost.
econdly, the convenience of never having to change the cartridges when ink used up- because they never run dry! This means you can carry on printing and refill the CIS at the same time. No need to stop in the middle of a long print run.