"I have an official Facebook page. I'm not on Twitter, Instagram," she tells PEOPLE.
"I have a couple of reasons," says the star of Men, Women & Children, who posed with costar Kaitlyn Dever for PEOPLE's behind-the-scenes portfolio at the Toronto International Film Festival.
"One, I don't want any more guilt coming from my phone or computer. I have the hardest time answering emails, anyway, so the last thing I want to feel is indebted to my phone or computer. So it's time."
"And the other is, what would I Instagram that people would want to see. There is nothing I would put out that people would want to see. It's probably best to stay away. They don't want to see me and my mom friends after kindergarten drop-off."
Eric Ray Davidson
For more of PEOPLE's exclusive photo shoots with Garner and Fever, Reese Witherspoon, Robert Downey Jr., Denzel Washington, Eddie Redmayne and more, pick up the new issue of PEOPLE, on newsstands Friday