Tennis is one of the few sports, if not the only sport in the world, where women can compete on almost equivalent terms with men as far as money is concerned.
From Forbes, highest paid female athletes of 2019:
"Tennis remains the most surefire way for female athletes to make millions of dollars. Witness the WTA Tour’s announcement last week that the year-end WTA Finals event will pay its winner $4.7 million this year—the largest payout in the history of men’s or women’s tennis. Total prize money on the WTA Tour is $179 million in 2019, and the ten highest-paid female athletes in the world this year are all tennis players (women from golf, soccer and badminton crack the next five).
Female athletes in soccer, basketball and softball earn salaries of pennies on the dollar compared with their male counterparts. The WNBA max salary slot this season is $117,500, compared with $37.4 million in the NBA.
Tennis remains the most surefire way for female athletes to make millions of dollars. Witness the WTA Tour’s announcement last week that the year-end WTA Finals event will pay its winner $4.7 million this year—the largest payout in the history of men’s or women’s tennis. Total prize money on the WTA Tour is $179 million in 2019, and the ten highest-paid female athletes in the world this year are all tennis players (women from golf, soccer and badminton crack the next five).
Female athletes in soccer, basketball and softball earn salaries of pennies on the dollar compared with their male counterparts. The WNBA max salary slot this season is $117,500, compared with $37.4 million in the NBA."
So of course, the best female athletes flock to Tennis. Men have more lucrative avenues than tennis. In team sports they earn a real salary no matter if they win or lose, instead of having to win matches and tournaments to earn the big bucks. Tennis is lucky to get the guys that couldn't make it in team sports. It's rare that tennis gets the best athletes. But guys like Federer, Nadal, Djokovic, could have probably played football if they wanted, but chose tennis. So on the other hand, if a man is one of the most successful in tennis, he can earn a lot in ambassador type contracts with some of the best known companies and make a tremendous amount, like Roger Federer.