Some plots are written around a sandbox element, especially if the dev is incorporating several subplots into one overarching plot. It gives the dev creative freedom to add/expand/complete characters that they feel motivated working on, and allows the player to pursue LIs they personally find interesting.
We already have 5 LIs (6 if you count Ava) in just the beginning phases: Sofia, Chloe, Scarlett, Sarah (completed), and Eleanor (completed). Bill and Linda are newer additions, and agent Adams looks like she's also going to be an addition as well. Luna is another one to get some attention in a few versions from now, so all of these LIs would make a more linear style of storytelling difficult to pace.