I might be wrong here (it's been a few days and I tend to mix up AVNs
), but in the beginning of the game, everything that is said about the MC - even in his own thoughts - point to him as not being a "great father" up until the start of the game. He refers to himself as a self-absorbed asshole who only cares for his own stuff and getting laid. His first reflections of Veronica are that he just uses her, for example. When you offer to take the daughter to the park, it's treated as an out-of-character choice.
So, I got the feeling that Allison's initial treatment of the MC is in fact well-deserved, and not just due to the cheating a few years ago, but also because of what happened since. From the point of view of Allison as a character, I don't find it hard to see why she would be suspicious of the MC's behaviour and lifestyle on the basis of the backstory.
It's obvious that her path was written to be a story of redemption and I don't think I've seen it that often in AVNs (I mean *real* redemption and not just manipulation
). For that story to be meaningful, you have to start at the lowest point in their relationship, so I guess that's why they wrote it that way.
I found her path to be very rewarding so far, especially when you get these small moments where her facial expression and demeanour changes for just a small moment and you can see that she's slowly but steadily building trust again.