Is Indian sandwich bread meant to always be grilled or toasted? In India, there are brands of commercially available white bread, specifically labelled and sold as "Sandwich bread". They are available as square and triangular shaped slices.  

These breads differ from the 'regular' breads in that they are rougher and harder to chew. So you can't simply start eating them even if you put some vegetables or mayo between the slices. It tastes and feels raw and awful.
The 'regular' white breads (sometimes called 'milk bread') are soft, sometimes sweet and can be eaten as-is; without even any butter or jam. Even commercially available brown bread is soft.  

I've also noticed that when "sandwich bread" is grilled, it becomes more 'chewable' and palatable. Sad part is, that many people I know, simply take "sandwich bread", put some raw cucumber, onion, tomato and capsicum slices between it and serve it to us.  

So my question is...are you aware of any requirement of rougher breads to necessarily be grilled before being made into a sandwich? Are they deliberately made rough so that they'd be able to absorb the wetness of jam or chutney?
As Jefromi already mentioned in a comment, the sandwich bread common in the Western part of the world is soft and often sweet, ready to eat.

When you search online for 'indian sandwich bread' you will only get images of roasted bread with various fillings.

I think the bread you refer to is in a half baked form, which you can find in supermarkets here sometimes too: it is used here mostly for baked sandwiches with cheese. The bread is only ready when going through another baking cycle.