Another way to phrase the question might be, "Why does the King James Version (and most other versions) translate two different Greek words as judge"?
ἀνακρίνω (anakrinō) - at least in this context - refers to "judging" in the sense of scrutinizing, whereas κρίνω (krinō) here refers to judging in a more final juridical sense.
The Orthodox New Testament suggests the translation:
But to me it is a very small thing that I should be examined by you, or by a man's day [ανθρωπινης ημερας]; but neither do I examine
For I am conscious of nothing in myself, but not in this have I been justified; but the One Who examineth me is the Lord.
Therefore cease judging anything before the time, until the Lord should come, Who both will bring to light the hidden things of
darkness and make manifest the counsels of the hearts; and then to
each one there shall be the praise of God.
The NASB also translates ἀνακρίνω as "examine".