There's no "special reason", other than that's the way the phrase can be used.
Incidentally, you can stand to lose things other than money:
Mr Forrest stands to lose his right to serve as a company director.
Now he stands to lose his right arm, affected by suspected gangrene
The phrase stands to lose simply means that a loss is imminent. Similarly, stands to win (or stands to gain) means that there is potential for some benefit, usually in the near future:
Proview Technology, which currently uses the iPad name on several of its products such as computer monitors, stands to win $1.6 billion and an apology from Apple, the creator of the iPad tablet, for allegedly infringing upon Proview's trademarked name.
This benefit need not be monetary:
With little standing between him and electoral triumph in November, he also stands to win an unprecedented fourth term this year.
The phrase is sometimes used in headlines, too, where the exact nature of the potential loss or gain is left unstated:
How Facebook stands to gain by sharing its trade secrets
Ukraine cabinet resignation resolution stands to win enough votes
Climate change: who stands to win and who to lose?
Sometimes the exact nature of the win/loss can be determined by reading the article; other times, a term like "stands to win big" is used simply as a way to say "will likely benefit greatly."