Well, in 1911 in at least our region, girls basketball was a new thing, and a quick overview of searchable Duluth newspapers tells me it was fairly controversial.

In Tower MN, a girls' basketball team had just been formed for the first time in 1911, and another brand new team had just been formed in Gilbert. In January of that year, the new teams were only practicing, and played other Range teams for the first time later that season. In Duluth, newspapers reported on games conducted between classes within the high school, which suggests that the girls teams were not yet playing teams from other schools. Possibly the idea of taking the train all the way up north to play teams on the Range was too far? Unimaginable given the controversy that they existed at all? In November, 75 girls turned out at Central for the basketball teams, and were told the rules of the gym, possibly for the first time. 

Duluth newspapers reported that year that in Sparta WI, the school board banned girls' basketball, saying it was "not conducive to good morals." In August 1911, Manitowoc schools did the same, saying the game was dangerous and "too violent to be beneficial or healthful to schoolgirls." In Biwabik in September, the board ruled to disband the new girls  basketball team, and a newspaper article in the DNT noted that there had been "considerable trouble over the team" the previous year. 

So, I would surmise that the postcard is a response on the part of enthusiastic local girls who were looking forward to the idea of actual school teams where they actually got to play other schools, which had not yet happened.