The only practical reason I can think of is for not loading objects that are absolutely NOT needed in the level at the time.
Let’s say you have a optional room with objects that the player does not have to go into, you can use soft object ref so you don’t have to load it with the rest of the level. That way, the loading level is small.
Or a clothing system with hundreds of outfits. Loading all of them at runtime will take longer to load than GTAV. With soft object ref. you load what you need.