Who uses zk-SNARKs?

Who are the primary users of zk-SNARKs in the world of cryptocurrency and finance? Are they primarily employed by developers to enhance privacy and security measures in blockchain networks, or do they have a wider range of applications and users? Are there any specific industries or sectors that frequently utilize zk-SNARKs for their operations, or are they used across a variety of different contexts? I'm curious to know more about the demographics and motivations behind the adoption of zk-SNARKs in the world of finance and cryptocurrency.