i think this passage explains why Jesus took on human form:

Hebrews 2:16-18 (kjv)

16 For verily he took not on him the nature of angels; but he took on him the seed of Abraham.

17 Wherefore in all things it behoved him to be made like unto his brethren, that he might be a merciful and faithful high priest in things pertaining to God, to make reconciliation for the sins of the people.

18 For in that he himself hath suffered being tempted, he is able to succour them that are tempted.

Or, in a more amplified way:

Hebrews 2:16-18 (amplified Bible)

16 For, as we all know, He (Christ) does not take hold of [the fallen] angels [to give them a helping hand], but He does take hold of [the fallen] descendants of Abraham [extending to them His hand of deliverance].

17 Therefore, it was essential that He had to be made like His brothers (mankind) in every respect, so that He might [by experience] become a merciful and faithful High Priest in things related to God, to make atonement (propitiation) for the people’s sins [thereby wiping away the sin, satisfying divine justice, and providing a way of reconciliation between God and mankind].

18 Because He Himself [in His humanity] has suffered in being tempted, He is able to help and provide immediate assistance to those who are being tempted and exposed to suffering.