Here are some points you could make and expand upon.
Sports, especially professional leagues, have become much more of a business. The players are expected to do so much more about keeping in shape, staying out of trouble and being professionals.
Way back in the day, athletes would play for a minimal salary and generally would have another job, sometimes in factories.
Most athletes these days go to college and get a degree because they worry about a post-sports career.
Sports have become a great way for high school students to get accepted into college and get scholarships.
Teams and pro players are more concerned about concussions and other injuries.
Their personal lives are so much more public now thanks to newspapers and, especially lately, social media. This leads to everyone hearing about both the bad and good things they do for society. Think of the recent events such as spousal abuse, deflategate, etc.
Hope this helps you get started! Sounds like a great topic.