Why American Sniper's Bradley Cooper split from model Suki Waterhouse

Update, 3/20:  A source tells E! that Waterhouse and Cooper "remain friends but they both want different things right now." While Cooper, 40, is looking to settle down and start a family, Waterhouse, at 23, wants to focus on acting first.
Original Post, 3/19: Suki Waterhouse and Bradley Cooper have split after two years of dating, E! reports. They began dating in March of 2013 and went public with their relationship later that year, when they attended the American Hustle premiere together. Just last month, Waterhouse joined Cooper at the Academy Awards, where he was nominated for his role in American Sniper. Both parties declined to comment on the split