Because Jehovah sees fit to waste everyone's time. Tell one person something, it is going to get distorted by the time everyone else hears it. This allows tyrants to hijack the message. It also means everyone is responsible for everyone else hearing the message. I could be in the United Tyranny of Stupidity minding my own business (as best the police state allows), and yet I am responsible for some small village about 50 km away from Jos, Nigeria or some isolated tribe located in the Republic of Central Africa if they don't get the message? When Jehovah could have just as easily told everyone at once, preventing anyone from missing the message.
Or, if you love tropical conditions, you might be minding your business in Singapore only to be held accountable for someone missing the message in South Georgia or the Shetland Islands, or some remote village in remote Siberia. Either way, Jehovah is trying to waste everyone's time, find excuses to deny happiness and fulfillment, and put everyone where they most hate. Worse, the whole message is going out of date--what happens when Agenda 21+ closes out all religion? What if the Age of Aquarius, coming in 2150, means the end of Christianity altogether? All that work spreading a fxxxing message, for nothing.