It's been five years since Arnold Schwarznegger and Maria Shriver separated due to Shriver learning of his affair with their housekeeper that resulted in a son. However, despite the length of time that has passed, the former couple is still married. Arnold and Maria: 5 Years Later…We're Still Married!!!, by TMZ Staff, July 17, 2016, tmz.com. According to the article, the parties have already worked out a property settlement and there are no minor children so there are no custody issues to discuss. One can only speculate as to why they haven't chosen to finalize the divorce, especially since both have moved on and are in other relationships. They are essentially living as if they are no longer married, but the failure to finalize the divorce may prohibit them from truly living separate lives.
First, and most obvious, so long as they are still married, neither of them can get married to anyone else. In Georgia, to be able to contract marriage, a person must "have no living spouse of a previous undissolved marriage. The dissolution of a previous marriage in divorce proceedings must be affirmatively established and will not be presumed." O.C.G.A. §19-3-2(a)(3). California, which has jurisdiction over the Schwarznegger-Shriver divorce, has a similar law. Thus, neither Schwarznegger nor Shriver can legally get remarried until their divorce has been finalized.
In addition, some insurance policies and retirement accounts won't let you remove your spouse as beneficiary unless there has been a final divorce. Often, you have to present the final divorce decree in order to change the beneficiary. Thus, if you and your spouse split up, but don't formally divorce, you may have to leave him/her as primary beneficiary. This means that if you die, your estranged spouse will be entitled to the proceeds from the insurance policy/retirement account, which may not be your intent if you are no longer together.
It is possible that Schwarznegger and Shriver don't care about the above issues, and that's why they are in no rush to dissolve their marriage. However, at some point, one may want to remarry and fully separate their financial lives and, at that time, they will have to move forward with finalizing the divorce.