Yes you make a good point. And those are written very recently, in the same language and notably are constantly being revised (which isn't happening with any religious books).
Instead people pick and choose the bits in the bible that fit with their real beliefs. Either writing off things as "not meant to be taken literally" or just simply glossed over.
This is an unfortunate truth, some Christians do pick and choose what to believe, but then again a lot of Christians, such as myself, that view the whole Bible as God's unfailable word and believe it all. Check out Answers in Genesis statement of faith. They believe the whole Bible is the Word of God. Not just parts of it.
The AiG Statement of Faith - Answers in Genesis
And many of our social standards and moral have come a long way since the old testament.
Imagine if there really is a god, how much you could piss him off just by meaning well but accidentally getting his instructions wrong!
How secure can you really be in your knowledge of any god's supposed will?
Food for thought I hope.
Actually if you read the Bible you'll see that God cares more about the heart of someones actions than what they accidentally do.
"But the LORD said to Samuel, "Do not consider his appearance or his height, for I have rejected him. The LORD does not look at the things man looks at. Man looks at the outward appearance, but the LORD looks at the heart.""
1 Samuel 16:7
"“Woe to you, teachers of the law and Pharisees, you hypocrites! You give a tenth of your spices—mint, dill and cummin. But you have neglected the more important matters of the law—justice, mercy and faithfulness. You should have practiced the latter, without neglecting the former. 24You blind guides! You strain out a gnat but swallow a camel.
25“Woe to you, teachers of the law and Pharisees, you hypocrites! You clean the outside of the cup and dish, but inside they are full of greed and self-indulgence. 26Blind Pharisee! First clean the inside of the cup and dish, and then the outside also will be clean.
27“Woe to you, teachers of the law and Pharisees, you hypocrites! You are like whitewashed tombs, which look beautiful on the outside but on the inside are full of dead men’s bones and everything unclean. 28In the same way, on the outside you appear to people as righteous but on the inside you are full of hypocrisy and wickedness. "
This last verse is Jesus talking to the Pharisees who were all about following the Old Testament law but whose hearts were unclean.
As you can see here God judges by the intentions of your heart.
"Some Pharisees came and tested him by asking, “Is it lawful for a man to divorce his wife?”
3“What did Moses command you?” he replied.
4They said, “Moses permitted a man to write a certificate of divorce and send her away.”
5“It was because your hearts were hard that Moses wrote you this law,” Jesus replied. 6“But at the beginning of creation God ‘made them male and female.’a 7‘For this reason a man will leave his father and mother and be united to his wife,b 8and the two will become one flesh.’c So they are no longer two, but one. 9Therefore what God has joined together, let man not separate.”
As you can see here the law of the old testament was given to show how sinful the people where. God gave the law to the people to show their sins, and to make it clear they needed a savior.
"19What, then, was the purpose of the law? It was added because of transgressions until the Seed to whom the promise referred had come. The law was put into effect through angels by a mediator. 20A mediator, however, does not represent just one party; but God is one. "
Sorry for all the long verses but I wanted to show the context of the verses.