Here's why:

* Porphyritic texture is defined by the presence of large crystals (phenocrysts) embedded in a finer-grained groundmass. This texture arises from a specific cooling process in igneous rocks where some minerals crystallize early and grow larger before the rest of the magma solidifies.

* Sedimentary rocks form from the accumulation and cementation of sediments, which are fragments of pre-existing rocks, minerals, or organic matter. The formation process doesn't involve the same crystallization mechanisms as igneous rocks.

In summary:

* Porphyritic texture is a characteristic of igneous rocks, not sedimentary rocks.

* Sedimentary rocks exhibit textures like clastic, crystalline, or biogenic, depending on the nature of the original sediments.