More and more expensive purchases start with a question to an assistant: which agency to hire, which clinic to choose, which software to compare. The assistant doesn't show ten links; it answers with two or three names. Being among them depends on what the AI has read about you and on whether your site can be quoted.
GEO doesn't replace SEO: it builds on it. Assistants query the search engine, read the best-ranked pages and quote the ones that answer clearly. That's why we work on it alongside SEO, not as a separate trick.