10 Reasons why would you get separation and not a divorce
If you are not absolutely sure that the marriage is over and need a time out.
If you want to maintain health insurance from one spouse to the other.
For tax reasons: There are tax advantages to being married and getting divorced could obviously have a negative impact on these benefits so you may want to defer divorce for a few months or years depending on the situation, but at the same time you do not want to be chained to an unhappy marriage so you separate.
For the children: You may be of the personal opinion that the children are better off if their parents are married and you want to defer divorce till they are no longer minors.
Immigration: Divorcing could affect your immigration status and thus you want to remain married though technically you may be leading separate lives.
Retirement benefits: You may need more time for your interest to vest in your spouse’s retirement plan.
Religious reasons: It may be against your religious beliefs to divorce so getting a separation is an option to assuage that guilt and the advantage of a separation is that you can remain separated indefinitely.
Health reasons: One partner may be terminally ill and the other does not want to divorce but by separating he or she can date other people and have a personal life without feeling like they are committing adultery.
Jurisdictional issues: It could be that the place you are living at the moment is not the best as far as the court system and you prefer to draw up a private agreement pending your return to a more familiar and acceptable jurisdiction.
Jobs: It may be better to be married for some jobs or at least appear to be married than to be divorced. For example, you may be principal ballet dancers in a major national ballet company and a part of your brand image is your marriage.