The reason behind the sandbox elements is so that the play can avoid content they don't enjoy. Every particular girl that the player can choose to interact with has a storyline and different kinks. After the first event for each of the girls, the player can decide if they want to continue interacting with them or not.
Sophia and Ava are somewhat of an exception because they're crucial for the plotline.
After this event with Ash (this update), the player can decide, "Okay, I don't think Ash's storyline is my cup of tea, I don't want her as a LI anymore, whatever." and not further their relationship. I want the same kind of thing with the other girls too.
But yeah, there are a few NSFW scenes, for now, most (if not all, depending on if you consider only NSFW as sex scenes) are with Sophia because she had a previous relationship with the MC before the events of the game. The rest of the girls are slowly being introduced.
The game's still in a very early stage of development. So, yeah. Do not expect a lot of NSFW scenes for now.
I hope this explains why the sandbox elements.