If you are separated but believe that there is a chance of reconciliation, then you should not get divorced (and you do not meet the legal standard to do so anyway).
However, if you are separated and you do believe that your marriage is over, then there are some compelling reasons not to wait to get divorced. This four part post will highlight the most compelling of these reasons.
Reason #1 Not to Wait: Cutting Financial Ties
So long as you are married, you have a financial link to your spouse. In Massachusetts any property that you hold either jointly or individually can be considered marital property subject to division by the family court. This means that if you acquire financial assets after your separation your spouse may have a claim to those, even if they didn't pay a dime to help you obtain those assets.
Similarly, if your spouse incurs debt after your separation, you may have some obligation to help pay that debt. This is true even if you had nothing to do with the items purchased.
The Court does not ignore the fact of your separation, and it may have a significant impact on how those post-separation assets or debts are divided. But the separation is only one factor among many that the Court must weigh. This means that until the divorce is filed, you are financially linked to your spouse whether or not you are physically separated (and whether or not you separate your finances).
Read Reason #2: The Ticking Time Bomb.