I think they help us to remember things because there are so many apps and tools that we can uise. Earlier, we used diaries and real calendars but now we can use digital ones, which can be more convenient for many people. Mobile phones are even more convenient because you just pull it out from your pocket and make a new memo wherever you are. You do not need to carry a diary or notebook with you. Physically, it is easier to have a gadget than to have a big diary or notebook.