I never understood it either. exW was in no rush to get the separation agreement and the divorce papers done. I had to push for both. The separation agreement was necessary to protect the custody and access to the kids. the D I pushed because I was done and she took her sweet time. she was already living with new dude for months now. never made any sense. like why are you dragging this out when you're done and moved on.
I have a separation agreement (had to push for this over a year ago) and after discovery was done my attorney advised me to stay married. This strategy worked because now he's interested in divorcing me. He requested the pre-trial and my attorney continued it just to be a pain.
It's also costing him a lot of money to stay married to me but honestly I don't think he cared about that. He'd rather go into massive amounts of debt than divorce me. It's mind boggling.