1.) Ankita sushant are working so hard due to JDJ and PR that Sushant doesn't even get to sleep at times. Look at his video in the IF interview. They really needed this break. In contrast, other actors who attended the function work in only one show.
2.) Its not just about singing the national anthem- it was a proper shoot. And every shoot takes time.
3.) They weren't informed by the production house on time and had made plans beforehand.
4.) They have been promoting the Republic day event on Zee TV
5.) They are singing the national anthem on JDJ this week
6.) Singing the national anthem on TV does not show that you love your country very much. Sushant choses to show his love and patriotism by teaching underprivileged children and supporting an institution called VOICE- this is a bigger, better example of service to the country.
7.) Going to a republic day function half-heartedly, when you wanted to do something else or take a break, or when you are too tired- with swollen eyes and tired mind, only to show your 'patriotism' is of no use. One should go with the right mood and spirit only. Jaana hai to pure mann se jao, warna NA jao. At least on Republic Day, people must be honest.