Because kilo- already has a meaning. And both usages of kilobyte were (and are) in use. If we are going to fix the problem, we might as well fix it right.
>>gizmo6+(OP)
Sure outside of computing in other science it has a meaning but in binary computing traditionally prefix + byte implied binary number quantities.
Many things acquire domain specific nuanced meaning ..
>>mc32+x1
Even in computing the binary definition is only used with memory sizes. E.g. storage, network speeds, clock rates use the standard definition.