* Scheduling conflicts: Sometimes, a show may be pre-empted by a special event or another program that has a higher priority. In these cases, the show may be moved to a different time slot or simply not air that week. Rather than leave a gap in the schedule, the network may choose to air a rerun of a previous episode.
* Production delays: Television shows are complex productions, and sometimes there can be delays in the filming or editing process. If a show falls behind schedule, the network may choose to air a rerun rather than risk airing an unfinished episode.
* Repetition for new viewers: Some shows, particularly those that are very popular, may air reruns in order to attract new viewers who missed the original airing. This can be especially effective for shows that are serialized or have a complex storyline, as reruns can help new viewers catch up on what they have missed.
* Cost: Reruns are generally cheaper to produce than new episodes. This can be a major factor for networks and streaming platforms that are looking to save money.
Ultimately, the decision to air a rerun is made on a case-by-case basis. There are a number of factors that can be considered, including the show's popularity, the availability of new episodes, and the cost of production.