This is a recent change in Facebook. It used to be that you can see all the posts of your Facebook friends unless it is over a certain amount of people. But there was a way to change that. But it is different now. Your setting is now where it shows the posts from people that you interact with the most. That comes to people that you have interacted with in the last 2 weeks.
You will not see posts from people that you have not interacted with in the last 2 weeks. Here is how to change it. Scroll down to the bottom of the news feed on the homepage and click on “Edit Options“, click on “Show Posts From” and change the setting to “All Of Your Friends and Pages”.
Even if you like the settings where Facebook has put them on your page, your friends will not be able to see your post if they have not interacted with you recently. But if you let them know about this, then they can change it and see the posts from all of their friends. This may not apply to all countries but it appears that it is like this at least in the U.S.A. and in Brazil.