It's the same way today with radio and TV programs. If the potential believer is not watching the right channel at the right time, or listening to the right station at the right time, the message won't be heard. Now, conditions are again fantastic for spreading the gospel. The Internet provides the greatest opportunity ever. Distribution is worldwide, and infomation is available 24 hours a day.
People worldwide can read anything else in the world.
I've communicated with people in Australia, China, Phillipines, South America, Latin America, Africa, Europe, Asia, not to mention people in nearly every US state. With barely more effort than already done for anyone using a computer, the gospel can be made available to millions of people worldwide for little or no cost. If you've written a sermon or lesson, usually the only people who will benefit are sitting in front of you upon delivery. With the net, modifying that information so it's available to people worldwide is relatively simple. The Home Site provides free sites in exchange for anticipated traffic, the more the merrier.