A 2016 study in the US revealed that 21% of people had been in an open relationship.
A 2015 survey revealed that 48% of British men and 30% of women were interested in one.
Scarlett shared her views with Playboy magazine in an interview published a month after she divorced Roman Dauriac.
Relationship expectations have evolved and some people are now in open or polyamorous relationships but not everyone has given up on the idea of monogamy just yet.
Joy Randolph - who is 25, married and monogamous - thinks Scarlett has got it wrong.
Joy has been with her partner for four years but admits she is the only one in her group of friends who believes in monogamy.
"The girls I know who are more into open relationships, they don't discuss it but you can see the signs," Joy tells Newsbeat.
"One of my friends never seems to commit, always seems to date multiple people at the same time but she would struggle to say she was into open relationships."
When Joy was single, however, her approach to monogamy and commitment was very different.
"When I was single I didn't sleep with multiple people at the same time but I also didn't commit either," she says.
"I would be with someone for a few months but I would give myself a deadline. I would have a nine-month rule.
"If, by the time the nine months were up I didn't see myself being with the person in the long term, I would essentially move on to the next person."
Joy admits she finds other people attractive but says she is "sickened to her stomach" if she imagines being with anyone other than her husband.
"Monogamy is a natural state for couples because when you find someone you really love you essentially give yourself to them wholeheartedly and you can't think about being with someone else," she says.
James Woolcock, a 21-year-old philosophy, politics and economics student from Exeter says he doesn't believe a "natural state" for any couple exists.
"It's probably what's best for individuals but on the whole, monogamy does seem incredibly stressful," James tells Newsbeat.
"The friends I know who have had monogamous relationships, some are perfectly fine and others have breakdowns, have the most stressful break-ups.
"I wouldn't say monogamy was unnatural, but it can lead to mental health issues if the couple doesn't work."
James has never had an open relationship himself, but many of his friends have successfully ditched monogamy for a relationship with fewer boundaries.
"It feels like they are far more easy going about what is happening with their love life," he says.
"That seems to bring them far more happiness and that's why an open relationship seems healthier."
But James Brumpton, a 27-year-old software tester from London who believes in monogamy says open relationships could be masking problems between the couple.
"I personally think if you're struggling to stay monogamous and you are starting to drift apart then maybe that's a natural sign that it's time to finish things or that your communication has broken down," he tells Newsbeat.
He says he would rather separate from a partner than try an open relationship, even though he knows others who have enjoyed an open relationship for many years.
"Some people are much more sexually fluid, they want to be more open and try things," he says.
James says every relationship needs rules and boundaries but that setting these in a monogamous relationship is always going to be easier.
"When it comes to monogamy the rules are a lot more clear," he says.
"When you have an open relationship the rules start to become a bit more grey."
Joy, who works as a success and holistic health coach, agrees and says that the problems in a monogamous or open relationship will only start if the people involved want different things.
"You have to be honest about how you truly feel about the situation," she says.
"There needs to be a lot of clarity and there needs to be a lot of respect because when you don't have that then people feel betrayed.
"It's really about having an understanding about each other and meet each other's needs.
"If you can't, maybe you're not supposed to be in that relationship in the first place."