Often as a DSL (domain specific language) for extending applications at runtime and/or configuration. I wouldn't start a "serious" project in Lisp today; meaning, a project with investment behind it, but Lisp can be a real joy to work with, and I've used Clojure for countless hobby projects. Clojure, in particular, has lots of deployments around the tech industry, and it's the foundation of the Jepsen DB test suite, Datomic (an immutable DB), and Metabase, as a few examples. Walmart has a non-trivial amount of Clojure running in prod as well.