because they arent in a shell.
Indians make a liquor called feni from the fruit.
The shell is inside the fruit.
From Wiki:
The shell of the cashew nut contains oil compounds that can cause contact dermatitis similar to poison ivy, primarily resulting from the phenolic lipids, anacardic acid, and cardanol.[3][19] Due to the possible dermatitis, cashews are typically not sold in the shell to consumers.[20] Readily and inexpensively extracted from the waste shells, cardanol is under research for its potential applications in nanomaterials and biotechnology.[21]