Photoshop eps and Illustrator eps are N O T the same.
The very definition of a vector is an algorithmic path that can be followed, such as a line, arc, or spline.
Raster graphics are predetermined dots of color sequenced together to form a photo or graphic. The dots are crammed into square inches. How many in a sqaure inch you ask? That's what defines dpi. There are no intelligent paths or vectors in this scenario.
The knife in your machine needs to be told what to follow. This can only be achieved by vector paths.
Photoshop is for raster graphics, Illustrator is for vector graphics. You can open .ai files in photoshop and if you watch the progress bar at the bottom of the window it says, 'rasterizing file...please wait'. It's turning what was once vector into raster for editing.