The arcane versions of those units have meaning only within the circle of people that actually understand them. Which makes them fairly useless other than for the purpose of being pedantic, wowing or misleading people. For the laymen, kilo means 1000, mega means 1000000 and giga means 1000000000. Having gamed on a machine when I was young that only had 64 * 1024 * 8 bits, I can appreciate the order of magnitudes here. Slightly over 0.5 megabit. But still. Who actually cares when a mobile phone might transmit that in a few ms (i.e. a few thousandths of a second).
Not to mention that these are frequently mixed up with non-SI units GiB and Gibit that are multiples of 1024 instead of 1000.
Storage size units are confusing =)