Why mix?

I ended up watching a show from India called Bollywood Unlimited, which is in English even though it covers the Indian film industry. They even have English subtitles when an Indian language (Hindi?) celebrity is talking to the media.

What I noticed, other than how different it is from American Hollywood shows, is that when the actors were being interviewed, they'd speak mostly in Hindi, but would occasionally throw English words in. Why do they mix languages? Why not just go for 100% Hindi? Is that common in India? I have no idea.

After a while, it was fun to listen to them speak while reading the subtitles, and try to figure out which English words they were using and how long they'd stick with them before slipping back into Hindi. I think switching between languages is technically called code-switching.

I can't find an extensive site for the show, but I did find a blog that has the same name, and it seems to have some good info (at least according to the poster's self-opinion) about what's going on there.