Part of this is just because people prefer a dramatic story, and "we prepared ourselves to overcome X, and then we found X and overcame it" is less dramatic than "we encountered all sorts of unexpected difficulties! and had to struggle to overcome them!"

The other part is a peculiarly English cultural tendency, particularly pronounced during the Victorian and Edwardian eras, to raise up for veneration losers who went down with style -- not just Scott, but figures like Gordon of Khartoum (http://en.wikipedia.org/wiki/Charles_George_Gordon) as well. There was a strong strain in the culture boys were raised in during that era that stressed chivalry and a particular sense of good sportsmanship as being much more important than whether one actually wins or loses.

There's a poem from 1892 called Vitaï Lampada (http://en.wikisource.org/wiki/Admirals_All/Vita%C3%AF_Lampad...), written by Sir Henry Newbolt (http://en.wikipedia.org/wiki/Henry_Newbolt), that is frequently pointed to as the best expression of this ethos:

   There's a breathless hush in the Close to-night --
   Ten to make and the match to win --
   A bumping pitch and a blinding light,
   An hour to play and the last man in.
   And it's not for the sake of a ribboned coat,
   Or the selfish hope of a season's fame,
   But his Captain's hand on his shoulder smote --
   'Play up! play up! and play the game!'

   The sand of the desert is sodden red, --
   Red with the wreck of a square that broke; --
   The Gatling's jammed and the Colonel dead,
   And the regiment blind with dust and smoke.
   The river of death has brimmed his banks,
   And England's far, and Honour a name,
   But the voice of a schoolboy rallies the ranks:
   'Play up! play up! and play the game!'

   This is the word that year by year,
   While in her place the School is set,
   Every one of her sons must hear,
   And none that hears it dare forget.
   This they all with a joyful mind
   Bear through life like a torch in flame,
   And falling fling to the host behind --
   'Play up! play up! and play the game!'

There is a line of historical thought that argues that this philosophy had a profoundly negative impact on British military thinking during the first half of the 20th century, with boys who grew up soaking in an emphasis on "playing the game" over winning becoming generals who presided over disasters like the horrific charnel-house offensive at the Somme in 1916 (http://en.wikipedia.org/wiki/Battle_of_the_Somme). There's a very good book (http://www.amazon.com/The-Rules-Game-Jutland-British/dp/0719...) that examines this exact question through the lens of how the Royal Navy fought the Battle of Jutland, if you're into this sort of thing.