Why did they cast lots?
Question: Why did Roman soldiers cast lots for the clothes of Jesus?
Answer: According to the Bible several people have cast lots (Leviticus 16:8, Proverbs 16:33, 18:18, Acts 1:24 - 26, etc.). Its main use was to render a decision not biased and based on human choice but letting God decide the matter (e.g. the selection of a replacement for Judas - Acts 1:24 - 26).
The use of the cast in public, however, determined an impartial decision based on time and chance.
Interestingly, though not commanded in the Bible, lots were cast to determine which of the priests at Jerusalem’s temple carried out a certain function like cleansing the altar or offering incense to God (The Temple at the Time of Christ, Chapter 7). They were common in games and gambling. Some of the things thrown were, depending upon the time and location, polished sticks, coins, cards, dice, bones, stones, etc.
Before the dividing up of our Savior's clothes, Herod's soldiers forced a gorgeous robe on him in order to mock him.
After Jesus went to Pontius Pilate, he again was forced to wear expensive clothing in mockery. The Bible is unclear whether or not this was the same garment previously used to mock him. He received his own clothes back after his torture by the Roman military.