I used Serp via API many moons ago. The most interesting part of the company imo is their legal defense of different plans:

  Production - $150
  15,000 searches / month
  U.S. Legal Shield

ie. "Our U.S. Legal Shield protects your right to crawl and parse public search engine data under the First Amendment. We assume scraping and parsing liability for customers on most recurring plans unless your usage is illegal."

I imagine at least some portion of companies use them just for this liability shield.