What is the deal with Pilot and Cartridges?

One of the things I think is very weird is how many of their pens that I’m interested come as a cartridge / converter pen instead of for example a piston filler. While they at the same time use a converter that don’t use the room available in the pen that well and have a boring line of cartridges.

If I get a Pilot pen, let’s say a Vanishing Point or a Falcon. Then I’ll use the standard cartridge, which I would have to use a syringe in order to fill it up properly, and I would still only get a fraction of the ink of a TWSBI Eco or a Lamy 2000.

Second, their ink line up. Pilot have some amazing ink, many if not all of them from the Iroshizuku line. Why aren’t they available as cartridges?

I don’t get it…