There is literally thousands of independent search engines that use Programmable search to search the entire web. Many ISP providers use it on their homepage, kids-based search engines like wackysafe.com use it, also search engines that focus on privacy like gprivate.com etc

Also LLM tools. Programmable Search Engine API was a way to give third-party LLM frontends the ability to give LLMs a web search tool. Notably, this was a common practice long before any of the major LLM providers added search capabilities to their frontents.