Facebook makes money on ads. While it wants you to succeed, thereby running more ads, Facebook also knows that most of us are just not going to go to the trouble of getting into our ad manager and taking the time to go through the process the best way for us. Consider the “Boost your post” like the stuff you find in the checkout lane. You’ll find gum and a couple candy bars, but not necessarily the candy bar you really like. But to get what you really like, you need to go back to the candy aisle.
The checkout lane is for impulse purchases. That’s what the boost button is for, too. Generally, you are better off (more bang for your buck) if you run an ad instead of boosting a post.