If "everyone" means "all US citizens" then startups can help increase transparency in government. It's much easier to figure out who to vote for when there's a clear picture of somebody's track record and who their political allies and funders are. Everybody should want this, regardless of political persuasion. If massive data gathering can't be stopped (and it looks that way) then the least we demand is real transparency. Without that there can be no accountability. Most political information people come into contact with is disinformation or shameless propaganda by some special interest. It is getting completely out of hand, but there's no obvious solution.
If "everyone" means "every person in the world", then we need startups to fight for sustainable energy and universal education. All scientific papers must be freely available to everybody in the world (few exceptions, e.g. how to manufacture anthrax can stay secret). Music and literature should be available to everybody, preferably at no cost. A single college textbook costs a month's salary in many parts of the world. That's just cruel.
There isn't much overlap between things that are super important for society and things that are profitable. The civil rights movement wouldn't work as a for-profit venture and future civil rights movements will be no exception. Often enough people who have contributed the greatest value to society never benefited from it personally. Duchesne or Flemming didn't get rich from their discovery of penicillin but the contribution to mankind is immense. In contrast the Bill and Melinda Gates foundation -- with their many billions -- struggle to make a huge impact. To really improve the quality of life across the globe a social revolution of some sort is needed.