Several companies do this. I already linked to Outdoor Herbivore and Zero Days. Trail Supply does it too. https://www.trailsupplyco.com/
You are right. They service multiple trails - the AT, PCT, JMT, and maybe the CDT and other hikes. Using any of these services is one way to solve the "I do not have someone to send resupply boxes" issue.
It also is one way to solve the health food dietary goals. Outdoor Herbivore can be thought of as an online health food store and shipping service option catering to health food conscious hikers demands rather than physically having to go into a bricks and mortar health food store.