Here's why:

* Organelles are specialized structures within a cell that perform specific functions. Vesicles are tiny, membrane-bound sacs that transport substances within the cell.

* Organs are made up of different tissues working together to perform a complex function. Organs are much larger and more complex than organelles, and they exist at the level of the whole organism, not within individual cells.

So, while vesicles are essential for cell function, they are not complex enough to be considered organs. They are individual components within the cell, making them organelles.