Fwb with ex?

[HalloweenIsGone]

I was surprised to see how common this was on another forum. Unfortunately my ex is a loser so not something I could consider but I definitely can see the perks to it! Is this a common set up for those that are separated?

My sister kept up a sexual relationship with her ex for quite some time after she ended the relationship. He was not able to cope with it and wanted more. I imagine one person would usually be holding out for a full reconciliation so likely to get hurt.
I’ve considered it with my ex (currently still living in the same house) but I think I’d be the one whose feelings were hurt in the end.