Why doesn’t a custom post type permalink ever hit index.php

Your Custom Post Type is using the single.php and (most likely) archive.php templates.

A single CPT post looks for templates in this order:

  • single-{post_type}.php – If the post type were product, WordPress would look for single-product.php
  • single.php
  • index.php

Other CPT pages look for templates in this order:

  • taxonomy-{taxonomy}-{slug}.php
  • taxonomy-{taxonomy}.php – If the taxonomy were sometax, WordPress would look for taxonomy-* sometax.php
  • taxonomy.php
  • archive.php
  • index.php