Short answer: The scientific and engineering community usually uses the metric system.

Long answer: Computers don't always use the metric system. Kilobyte has two meanings. Sometimes it means 1000 bytes, sometimes 1024 bytes. This is because 1024 is 2 to the power of 10 and powers of two are "round numbers" for binary computers. It's easier to build a computer that has a memory size which is a round number so they'd often have sizes like 32768 bytes (2^15). This would be represented as 32KB first as simply an abbreviation and approximation in the same way we might say "That computer has 32 thousand bytes of memory" rather than giving the exact figure but by around 1965 people had started using KB to mean 1024 bytes.

Obviously this has caused a lot of confusion over the years, resulting in a number of court cases, and while 1 kilobyte=1000 bytes has become the standard in most places there are still some where 1024 is the typical usage. For instance when buying RAM 1 gigabyte usually means 1024*1024*1024 bytes.

Just to make things even more confusing, it's uncommon but not unheard of for a measurement to use 1000 until the final kilobyte step and then use 1024 for that. For example a 1.44MB floppy disk stores 1440*1024 bytes.

These differences in measurement are the reason that you will sometimes buy an 80GB harddrive and then find that your computer reports that it's a 74.5GB harddrive. Harddrives are sold in 1000 units and reported by your operating system in 1024 units.

In 1998 the International Electrotechnical Commission attempted to sort out the confusion and said that kibibytes, mebibytes and gibibytes would be the new names for the 1024 units and that they would have symbols of KiB, MiB and GiB and while it's pretty much unheard of to hear the full names, you will sometimes see the KiB form when someone want to be careful to be specific. They also specified that the normal names should ONLY be used to refer to the 1000 units but this has been widely ignored.