Hi. I am not sure I completely understand your question.
The Earth, Sun, and Moon do not orbit on quite the same plane so the don't line up in a perfect line very often. That is what you need for an eclipse.

Are you asking why other things passing between us and the Sun don't cause eclipses? That's because most other things that pass between us and the Sun are either too small (like spacecraft) or too far away (like Venus and Mercury) to cause a full fledged eclipse. It is still possible to see them going between us and the Sun, though. They look like small spots. That is called a transit. There is a transit of Mercury coming up next month, although you would need a special telescope to see it.

Terry