It's annoying when your brain won't switch off!! We need sleep for the brain to function, but there's too much to think about apparently.
Good question.
The way I see it, God had two periods of time when he had active prophets and had their words recorded, not just for the people of the time, but for us in the future.
The first was when Israel was formed into a nation. After their release from Egyptian slavery, they promised to obey the laws God gave to them. At Mt Sinai, He offered the nation a covenant (legally binding agreement) through his prophet Moses, that he would guide and protect them as long as they kept his commandments. They agreed to this and were bound by it as a nation.
Their forefather Abraham was also in a covenant relationship with God, who promised to produce the awaited Messiah in Abraham's family line. So Israel's history was recorded for posterity as part of the 'all scripture that was inspired of God and beneficial for teaching and reproving and setting things straight.' (2 Tim 3:16, 17) It it the measuring stick for all things and a record of what is expected of those who claim to worship the Creator.
God's blessing on Israel when they obeyed, resulted in a periods of peace and prosperity. But when they disobeyed (as they did often) his punishments were sometimes quite severe. But he never abandoned Israel because of his promise. According to God's timetable, the Messiah came to his nation...but what spiritual condition did he find the nation in? A very poor condition as it turned out.
It had been approximately 400 years since the last prophet was sent to correct God's people and now it was time to correct them again. But the Messiah was not just sent to Israel as a nation...he was sent specifically to "the lost sheep of the house of Israel". We know that Jesus particularly targeted the sinners who had basically given up trying to keep God's law...or at least trying to keep the Pharisees very rigid interpretation of the law. Their oral traditions had all but buried the spirit of the law in their impossible legalities. Jesus came to lighten their load and to refresh them spiritually.
But he didn't fit the Pharisees expectation of the Messiah who in their mind was going to be powerful political leader who would liberate the nation from Roman oppression and establish his kingdom over Israel. They believed that this would elevate their status and set them up for positions of power in the kingdom.....how deluded they were!
So until Jesus came, Israel had been without prophets to correct them for a very long time. The spiritual derailment was obvious to God's son and when his ministry began, he was treated with skepticism at first. After a while though, the Pharisees realized that this Jesus was speaking against them and their teachings, so they began a campaign of defamation and persecution against him and his followers. Jesus told his followers to expect more of this. (John 15:18-21) We all know how it ended.
Jesus and his apostles were the last prophets that God sent. Again, the activities and teachings of these prophet were recorded for our benefit. Then the window closed. An apostasy was foretold and it happened just as the scriptures stated.
The complete word of God is the Bible. We do not need any other instruction......but we do need help in understanding it because of the deceiver's attempts to corrupt its teachings. Jesus warned about this in his parable of the "wheat and the weeds". Christianity was going to be corrupted in much the same way as Jusaism was. Jesus said that men would introduce their own ideas and teach "commands of men as doctrine". The weeds were not sown recently, but go back centuries. Most people have no idea that their worship is futile because it is not truth. Just as the Jews were convinced by their religious leaders that the truth was a lie, so the devil has duplicated his deception on Christendom.
When Jesus comes as judge, he tells these "Christians" who believe that they are doing good works, that he NEVER knew them.....NEVER means NOT EVER. So from its inception with Roman Carholicism, Jesus has never recognised Christendom as Christianity. It was corrupted from the beginning. This is why he calls them "workers of lawlessness". (Matt 7:21-23)
The propensity in man to introduce things into their worship that do not belong is a recognised and an often repeated trait, so having one set of rules and one set of teachings via a written record instead of oral transmission greatly reduces the danger of the "Chinese Whispers" syndrome.
Add to that the propensity for the deceiver to add his own prophets into the mix and the situation would be worse than what it is now! Without some kind of reference from God himself, how could we ever make a decision about who to believe?
We are given choices about worship. Our own hearts determine what faith, or lack of it, we choose. God is reading hearts every day, so he is having his message preached in all the earth, "searching" for the "worthy ones" so that people can choose to accept the message or reject it. (Matt 10:11-15)
Just as some of the people in Jesus' day were not put off by the weight of public opinion, and the defamation put out by opposers, so people today are in the same boat. They were an unpopular and persecuted minority, but Jesus said that if some listened to him, they would listen to his disciples too. (John 15:20)
JW's are out in the preaching work every day, in every nation, but we aren't expecting a mass conversion......we will keep offering the message until "the end" just as Jesus said. (Matt 24:14)
We just hope that some respond....but we are not depressed or upset when they don't because Jesus said we had to "shake the dust off our feet" and keep preaching.
This is what we do......