People argue about whether putting stuff on arxiv constitutes "publication". I like the loose definition of publish (it's available for a wide audience to read, with at most, pay barriers) but other folks do not. There is still a huge cachet in being able to point at a peer-reviewed paper in a prestigious journal, no doubt, and many people will consider arxiv a preprint server, not a publication.

(in the old days, after your article was accepted, but before it was published, they'd send you a few copies labelled "preprint" that you could distribute informally)