This is partially true. The stigma is not so much against carrying your own food, as it's against carrying the particular type of tiffin box that is shown in this video. They are quite large and bulky. Imagine, a guy in a suit, with an Attache in one hand, and the bulky tiffin box in the other. Also, if you commute by Mumbai's local trains, it will be a nightmare to board them with the boxes. Here's a snap taken inside a typical coach: http://www.mumbai77.com/Pictures/Gallery/displayimage.php?al...

But Shahrukh Khan carries his plastic tiffin packed by Anushka Sharma to work in Rab Ne Bana Di Jodi and his coworkers are in awe!

That scene is from a small Punjabi town. It is difficult to carry lunch boxes in Mumbai's local trains.