It's an easy, believable way to show semi-decent renders at the start of the game and it can be used as an opportunity for sex later in the game. It's the same as the wet dreams some games have so that they can show lewd content early without fucking up the story.
The concept is known as "filler".
You add it in whenever you need an excuse to fill your game with a few extra shots of your models in "sexy" poses without needing to waste any effort on actually moving the plot forward in a meaningful way. Just a little extra lowkey padding to extend the average play time (making it look like your game is longer is generally something most devs want to do) and usually the players wont complain because sports bras and yoga pants are hot.