cp/m had tools for using floppy disks (and so did ms-dos) being able to save your work to a floppy is basically a necessity. There were "encode your data/programs onto a cassette" and some paper tape, but those were incredibly inconvenient. . To use floppy disks you needed to format them, have some notion of a filesystem, be able to DIR and COPY files, and programs like word processors needed a way (a standard way, a single way, etc.) to talk to the disk to open and save files. That's what cp/m did.

cp/m from the user perspective (command line) was something of a knockoff of Digital/DEC command lines similar to RSTS or RSX-11 (probably RT-11 too? never used it)--PIP ftw! These are somewhat similar to MSDOS command lines. Unlike unix "everything is a file", these operating systems had the notion that "everything's a device" (like MSDOS things with colons, CON: AUX: LPT(?): etc., and sometimes "we'll provide the baling wire so different devices can talk to each other but it's not guaranteed", COPY A:FILE LPR:

PIP (peripheral interchange program) was the workhorse that actually did it all underneath, PIP A:FILE.DOC LPR:/COPY to extend the example above. I think that they actually may have put DEST: before SOURCE: and maybe DEST:=SRC:, and maybe the /COPY had to be on the dest, i don't remember, but for this purpose it's "eh"

basic does not offer anything like that. It could have, but for whatever reason, nobody thought to add those features, they were probably thinking more along the lines of "we're in ROM, why would we need a floppy? feature!"