Why are soap Teaser Trailers used?

For our A2 media project, we have to create a trailer introducing a new soap. Soap trailers are incredibly important in the world of media as they entice in existing and new audiences to watch the on going soaps. Teaser trailers for soaps let audiences know when something exciting or dramatic is going to happen in the soap without giving away the actual story like. Normally the theme of the storyline is suggested.
Below are some soap teaser trailers that I particularly like:

This advert is for the very first series of Skins, we like this advert as its fast paced, young and idolises every teenagers dream of 'sex, drugs, rock and roll' My favourite part of this advert is the close ups of the slow motion scenes that fit with the pace of the music.

This advert is very different to the Skins advert, it's almost a behind the scenes look on Hollyoaks, again it is fast paced, it's up beat and fun. However the more we watch this trailer the more we dislike the upbeat idea, we prefer the darker side of the soaps like the Skins advert. 

This is the Being Human series 3 trailer, its dark and quite comical towards the end. The light verses dark in the different scenes works really well, you also get a good sense of the three main characters.

And we also researched existing A Level Soap Opera trailers, our favourite is one called This Life:

We love all the different camera angles, the dark colours used and the story lines of pregnancy, drugs and the breaking  into a house. They are very simple story lines but the angles and camera angles create a brilliant A grade.