The problem is the vast amount of computer code and documentation that uses kilobyte=1024. In fact even today most memory manufacturers use the power of 2 notation. Pick a random datasheet for a DRAM chip, a microcontroller, an EEPROM or flash memory and I guarantee they will use powers of 2 and the "old" words like gigabit or the "MB" suffix.
It would have made a lot more sense to define new words for powers of 10. Kibibyte = 1000 bytes etc. Only hard drive manufacturers would have been mildly annoyed, until they realized that they didn't have to print "1GB = 1,000,000,000 bytes" on the label any more.