Let's talk about the reasons for the popularity first, hehe. For example, Hunan Satellite TV, isn't there always a fluttering program preview at the bottom of the screen? The title of the book will be used when listing the songs. At least TV stations, editors of punctuation marks and the like should not make mistakes ~ ~ ~
Next is the official reason. Is the use of the title. There are some in Baidu encyclopedia.
Book title (double title: ",single title: < >) is a symbol used to represent book title, article name, registration, file name, drama name, song name, picture name, etc. The title of a book indicates the name of a book, document, newspaper, article, etc. , but also used in songs, movies, TV dramas and other literary and artistic works closely related to the written media. When there is a title in the title, the outer layer uses a double title and the inner layer uses a single title. If there is a title in a single title, use a double title in a single title.