There are many sports that make money on their players. But players can use Instagram to help them increase their marketing. By having pictures of themselves taken during games and practice they can increase interest in themselves at contract signing time. Or they might get more money when they had an endorsement from a company.
There are sports with limited exposure except for ESPN 8. So these stars are needing to market themselves to increase interest in the sport and themselves. Instagram can be a great marketing tool.
When a person that is in a sport that is not a major player their is still money to be made but not millions. The only thing is that they do not want to do things that will make them self or their team look in a bad light.
So if they start to use Instagram they can get their name out their and it is done mostly by showing them in their sport. From their they can get information about their name out for fans and for potential agents and business opportunities. They might also be able to make a second carrier after they are done playing their sport.