The game is a slice of life but there's a lot that happens off-screen/a lot of brief time skips. Even with that in mind: I'm not sure why you're acting as if there aren't several scenes that clearly shows them all having food together. The MC is absolutely making sure they're well-fed.
For examples, there's the scene of Liv eating pizza in Ch1, the breakfast scene in Ch2, in Ch3 the MC comments about keeping lots of food in the house now that they're living there and we see Maddie eating popcorn, in Ch4 we see Liv having a donut for breakfast and we only learn that they're out of money after they go to the snack shop by the lake, as prior to this the MC believed they still had some. We then see them with an entire picnic basket filled with food/having lunch while sitting by the lake. In Ch5 there's comments about them having already eaten/had dinner. In Ch6 we see the MC grocery shopping and cooking food with Maddie/sitting across from her while she eats. In Ch7 we again reference them eating off-screen.
So yeah, it's not that the girls aren't eating/well-fed: but rather that we just don't always see it because our MC is busy doing his own thing/on his own schedule and the girls are independent enough to feed themselves. He keeps food in the house and they didn't have to "beg" for sweets at the lake, lol. We literally offered when we learned they were out of money.