Shock advert for anti smoking

This is the new UK government's anti smoking advert.  It uses shock advertising to explain that cigarettes cause tumours to grow in your body.

1) Why would audiences engage with this advert?

2) How does it represent smokers?

3) Why does the government rely on shock tactics for campaigns like this?

4) How have they used mise-en-scene to communicate a message about the lifestyle of a smoker?