Women: If it please you good sirs, might have we have the vote?
Women: We deserve the vote. Can we please have the vote? [Women hold rally to garner support]
Men: No. [Men monitor the rally, report to authorities on dangerous lady organizing.]
Women: [Throwing a rock through a window on a crowded street] Give women the vote!
Men: Criminals! You don't deserve the vote! [Men arrest women]
Women: [Testifying before male lawmakers] Please sirs, can we have the vote?
Women: Vote for Women! [Woman throws herself in front of horse, eventually dying, in protest of unequal laws]. Can we have the vote now?
[Credits begin to roll, including a timeline of the dates women received the right to vote in various countries. 25 years after the events in the movie, women received the right to vote in the UK].
In all seriousness, that the film crops this particular segment of history - a group of working class women trying various tactics to achieve equality and ending with them, tragically, still not having the vote - serves three important purposes.
One, it counters the Great Man Theory of History whereby individual men (and it's almost always men) are entirely responsible for important historical events and movements. In Suffragette, no one person is presented as being predominately responsible for equality, including the female protagonist. Were this a movie about male advocates, we would been presented with a male main character who was explicitly heroic, as though he were almost single-handedly responsible for making history even if, in reality, success was achieved through many people's efforts.
Two, the movie shows that no matter where one's social justice tactics fall on the spectrum of civil to uncivil, a segment of one's opponents will always remain in opposition. In this case, a generation of men in power believed women shouldn't vote. Period. And so, women couldn't vote. The key seems to be to figure out which groups within the opposition are capable of changing their minds and saying to hell with the rest of the ones who will never change their minds. (When you figure out how to do that, let me know).
Three, by ending with women still not having the vote and then rolling the credits of when women throughout the world have achieved the vote, the film suggests that the fight for women's equality is not over. Indeed, women are still achieving suffrage rights into the 2000s. Had the film ended on an uplifting scene of women celebrating their equal voting rights, I think it would be tempting for some to think, "Welp, women's equality has been achieved, Next issue, please."
In reality, any time certain populations are categorically excluded from suffrage, I think their exclusion will most immediately impact who is and isn't elected to office. Even after excluded populations achieve suffrage, their prior exclusion will also have lingering effects on conceptions of who is and isn't appropriate for political office based on historical models of "what elected officials/leaders look like."
Hmmm, seems like this concept might still be relevant today.