In Egypt they are allowed for wreck dives, but not for almost all other dives. Because you do not wear gloves, you are less likely to grab something and therefore the reefs are better protected. The use of knives is also limited because divers in the past used them to, for example, remove an arm from a starfish and feed it to another animal. It’s a shame but true and that’s why the use of knives and gloves is generally prohibited on liveaboards. If you still want something to cut a line, take a line cutter with you. If you have to wear gloves for medical reasons, ask your doctor for a statement and everything will be fine.