Among other things, it gets used up, it may become too fine to cut the kerf at that IPM, it may also have impurities, etc. Depending on the abrasive, it's theo

Among other things, it gets used up, it may become too fine to cut the kerf at that IPM, it may also have impurities, etc. Depending on the abrasive, it's theoretically reusable, but that would be very hard to quality control (even assuming you separate it effectively from the material). This is one reason waterjets often get used only when other ways of cutting are not effective. Also note: for things like wood, you can probably water jet them without abrasive.