i don't know how many times it has to be said that coding can be finished with placeholder art, there is no reason to wait for all of the art and posing to be finished first.
I'd guess it's a matter of finance. DC usually doesn't do any real placeholders but draws his more detailed concepts right before he draws the final image, especially since he's often changing details according to feedback on picarto.
In addition working with placeholders will cause additional working hours which will have to be paid for in the end. DC seems to avoid every bit of work that is not productive, hence no placeholders, no old savegames, etc.
Nah. Mom will have scenes in future updates. Its just the last this year.
Well, I doubt there's going to come much more when it comes to actual H content. She'll get most of those scenes (cinema, car, TV, MC's new dream, etc.) this update and all that's left is going to be the actual story and scenes related to other characters. In the end DC seems to have pretty good idea about what he wants to achieve and won't add things which don't fit into his plan.