Here's why:

* Packaging and Modification: The Golgi apparatus acts like a processing and packaging center. It receives proteins and lipids from the endoplasmic reticulum (ER) and modifies, sorts, and packages them into vesicles.

* Vesicle Formation: These vesicles, containing the packaged materials, bud off from the Golgi.

* Fusion with Plasma Membrane: These vesicles then move towards the cell membrane and fuse with it, releasing their contents outside the cell – this is exocytosis.

In summary: The Golgi apparatus is the key player in exocytosis, ensuring that the correct substances are packaged and released from the cell at the appropriate time.