A newspaper article on the teenage job market mentioned several possible reasons for the shortage. They said the main reason was that older people had these jobs. There was no mention of another reason.
Teenage jobs have historically been such things as stockroom people, bussing tables and other restaurant work, landscapers and other pick & shovel construction positions.
Those positions are in great part currently filled by immigrants – illegal and otherwise. It is clear that this factor plays some part in the availability of positions this segment of the job market. Count on the media ignoring things they don;t want to talk about. It hurts the credibility of any article - if it can be hurt any more.