The movies that you are talking about depict the average middle class educated Indians. This demographic talks in a mix of Hindi, English and sometimes a regional language even in their day to day life. The movies just depict the language spoken by this demographic.
Also, most Indians are bi-lingual (some can speak more languages) but an average American speaks only English. Hence most Hollywood movies only have English spoke in them.
Bollywood movies based in villages do not have people speaking English in them 