Reputation and responsibility
Being an coauthor of an article contributes to your reputation as a researcher, as publication tracks are also considered for funding and tenure.
Here we also see a direct consequence of the order of the authors. As in-text references to articles with many authors sometimes consists of only the name of the first author and the abbreviation et al., the name of the first author is more prominent in the literature (Brand, Allen, Altman, Hlava, & Scott, 2015).
An author of an article, however, is also considered responsible for the content of the article.
As worded by the ALLEA code “Authors are fully responsible for the content of a publication unless otherwise specified” (ALLEA, 2017, p. 7).
In practice, however, not all co-authors are always considered fully responsible.