One aspect of this site is that sometimes questions can lead to spoilers. It's an inherent danger to any topic regarding a movie or tv series. With movies it's fairly easy to avoid, as each movie has its own tag, even amongst movie franchises, and questions regarding events are usually tagged.
While we try to hide spoilers in titles, sometimes this means the titles are so generic that someone half way through a TV series will end up reading, or attempt to answer it.
If we used tags for Seasons, like we would individual movies in a series or franchise, we could avoid this. While a bit meta, this may alleviate some issues with user participation. (I.e., someone can participate on questions regarding seasons they have seen while ignoring seasons they have not). And it's functionally the equivalent of movie series tags. For example, someone can avoid Star Wars Episode 7/The Force Awakens spoilers by ignoring that specific tag, while still seeing other Star Wars questions. The same can't currently be done with Game of Thrones, or Agents of Shield, or any other long running series.