Well, yes, in the past, sure. But seasoned, contemporary Lispers, actively using Lisp to write programs don't usually do that these days, unless they are referring specifically to things like CLISP, XLISP, AutoLISP, etc. Even Common Lisp is no longer capitalized in each letter anymore. You can use whichever style you like. But just so you know, some Lispers may get annoyed.

But then again Lispers often get easily annoyed. Some of then get annoyed when you say "Clojure is a proper Lisp".

While that is all true, those old books are still useful and good, and by and large much better than newer books.

That could be one reason why newcomers still keep using "LISP".

Come to think of it, there must be people using "LISP" who were not even born prior to the first time (or even the umpteenth) someone was corrected in this matter on the Internet.

People who will one day write "LISP" into an online comment are not yet born, or still in diapers.

Maybe we need to target preschools and kindergartens?

Even the source code in the past was all caps...

LISP usually signals: the Lisp of the past is included.

Lisp then signals: Lisp since lowercase keys on keyboards were introduced ;-)

CLtl1 used "LISP" in a special capitalized way. CLtL2 then used "Lisp" for the same text.