Why do female stars over 40 agree to be in blockbusters?

The big-budget world of the blockbuster franchise has typically been somewhat closed off to women of this ilk while their male counterparts still dominate. Robert Downey Jr (50), Johnny Depp (52), Tom Cruise (53) and Will Smith (47) are all seen as viable and profitable names to hinge major properties on, but aside from perhaps Angelina Jolie, it’s only younger women who are allowed to compete.
 Even then, we’re mainly talking about Jennifer Lawrence and Scarlett Johansson, who is still to receive her Black Widow movie though. Now this latest trend of hiring inarguably overqualified women to take on roles in action sequels is hardly evidence of a total sea change.