Purpose of a Title Sequence

A title sequence is the method by which films present their title, key production and cast members.

The purpose of a Title sequence is to show the audience who the cast and the crew involved in the production are. Film openings are used to show the company who the production was made by and also the main cast members.
A film opening can attract an audience by engaging the audience with what is to come within the film, leaving the audience watching because they're curious to know what the film is going to be about. By having the main cast members appearing on screen gives the audience some knowledge of who will be in the film allowing the audience to decide whether the film will be good depending on who will be in it.