Why cant I send my printer with its ink catridges inside on a plane ride?

Well I wanted to deliver my printer to another country using their air delivery service. However, DHL wanted me to take out the ink catridges. Why is that?Why cant I send my printer with its ink catridges inside on a plane ride?
Ink is flammable. There also may be some issue with the pressure causing a leak.Why cant I send my printer with its ink catridges inside on a plane ride?
...and inks are considered liquids/gels and those are no-nos unless they are in a 1qt bag...wonder how much Ziploc paid for THAT.

oily skin