News organizations that use wire services have contracts with those services that dictate how they use their articles. Often they contract the wire agencies for only certain type of content, and the price depends on how many categories and how in depth of content they want (e.g. full articles cost more than ticker lines). The details can vary, but usually articles ran verbatim are attributed to the agency, while articles that are merely based on articles from the agency are not attributed to the agency (in part to protect the agency in case the article turns out to be incorrect or etc.) but instead include a note at the end that they use content from the agency.
For articles run directly, it's part of the nature of those agencies and their contracts with their writers that the byline goes to the agency rather than the original writer (which is often multiple people anyway). This attribution is so common that back when newspapers were set in lead, and still sometimes today, a special ligature was used for AP, and sometimes for UPI and AFP as well.
Newspapers also sometimes run content directly from other newspapers, in which case the byline will list the author and original paper---and this is done under a contract with the other paper, either money changes hands or sometimes it's a mutual sharing agreement.
For articles run directly, it's part of the nature of those agencies and their contracts with their writers that the byline goes to the agency rather than the original writer (which is often multiple people anyway). This attribution is so common that back when newspapers were set in lead, and still sometimes today, a special ligature was used for AP, and sometimes for UPI and AFP as well.
Newspapers also sometimes run content directly from other newspapers, in which case the byline will list the author and original paper---and this is done under a contract with the other paper, either money changes hands or sometimes it's a mutual sharing agreement.