We don't want people who aren't well-versed with how Stack Exchange works making tags willy-nilly.
The general guidance is to use the closest tag you can and include text in your question asking for the tag to be created. A user with sufficient privileges can take care of that and remove the text at the same time.
Of course, one hopes that the lack of an ...
If there was a web app called "Question and Answer" then the tag would be a good fit and need to be created for questions about it.
But since the example here is a tag based on a broad topic matter instead of a specific web app or website, it would not make a useful tag to have or create.