The Smith Morra gambit has one of the highest win rates for white at below Master level.
...as well as the highest percentage of patzers employing it, which explains the high win rate.
Not following the logic here. If patzers are playing the Morra, why are they winning so much?
Most of the play e5 repertoire books give Capablanca's idea, probably due to economy since it can be used against the Goring as well, and it's such a simple idea that not many pages need to be written about it.
But White does have some 10th move alternatives, and if the player as Black is higher rated they're faced with a dillema, should they accept the gambit and allow the tactical complications which give a lower rated opponent the best practical chances to win? Or should they use Capablanca's defense and get a drawish position? In most cases a higher rated player would have better endgame technique, but the familiarity the Danish Gambiteer has with the position could make up for this and assuming they've studied and played games in it they'd likely be able to hold the draw.
The Danish is a good opening to have in ones back pocket either for fun games against friends or for serious games against higher rated opponents.