Probably because Common Lisp is already on a similar level of being data-centric, so it would be redundant to talk about it. Actually, the only difference between how Clojure and CL treat data is that (while both offer access to both kinds of data) Clojure strongly prefers immutable values, while CL doesn't care.
Clojure doesn't just "strongly prefer" immutable data but syntactically ensures that all data is immutable unless governed by one of four concurrency mechanisms. Persistent data structures aren't just a popular convention in Clojure--the language is literally built around them.
Probably because Common Lisp is already on a similar level of being data-centric, so it would be redundant to talk about it. Actually, the only difference between how Clojure and CL treat data is that (while both offer access to both kinds of data) Clojure strongly prefers immutable values, while CL doesn't care.