Depends on what you mean by space.
I like my own bed space, bedroom space even.
I also like my own space as in not having to think of someone else before myself 100% of the time. Nothing better than just sitting in your own space every now and then.
Can't be doing with living in each other's pockets just because you are a couple.
But all the above can be done within a relationship, splitting up and having space might be an excuse for some, but it could also make a couple appreciate each other more