Why does the Bible seem to condone slavery?
The Bible is mostly ambiguous about the morality of slavery. Several passages do seem to condone slavery by giving guidelines for the buying, selling, treatment, and required behavior of slaves.
"Here are some other instructions you must present to Israel: ‘If you buy a Hebrew slave, he is to serve for only six years. Set him free in the seventh year, and he will owe you nothing for his freedom. If he was single when he became your slave and then married afterward, only he will go free in the seventh year. But if he was married before he became a slave, then his wife will be freed with him. If his master gave him a wife while he was a slave, and they had sons or daughters, then the man will be free in the seventh year, but his wife and children will still belong to his master" (Ex. 21:1-6).
"Slaves, in all things obey those who are your masters on earth, not with external service, as those who merely please men, but with sincerity of heart, fearing the Lord" (Col.3:22 NASB).
God's perfect will would be that all men be free, but the Lord does not run the affairs of world governments. He has given man free reign to do what is right in his own eyes. The Almighty will someday rule on earth, but for now His role is to act as an advisor to mankind.
A very good reason the Bible doesn't focus on forced servitude is that slavery of the mind to sin is a much bigger problem than the imprisonment of the body. It is meaningless for someone to gain physical freedom and lose his eternal soul.
"If the Son therefore shall make you free, ye shall be free indeed" (John 8:36).