हम हवाई जहाज़ उड़ाने वाले, फिर भी फ़िदा हैं, पटरी में दौड़ने वालों पे. - SK Mangla

A train becomes desirable by having atleast one of the following features:
1) Very good schedule
2) High speed
3) convenient departure and arrival time
4) cheap fares
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Most successful trains will have one of the features, and many have more than two.
Humsafar, except for some like Pune SRC have none :p
GR certainly has point 4, and in many cases 1,2 and 3 as well. Successful rajdhanis have 1,2 and 3 but fail on 4, yet are still quite successful.
Humsafar as a concept has nothing to do with passenger comfort, and everything to do with money grabbing, and in price sensitive market like india there was bound to be failure for such scheme.