I think David pretty consistently took his personal commitments to others very seriously. He was never going to lose that carefree attitude all together (which I can totally see could get infuriating at times), but he would be there when it really mattered, ready to make hard sacrifices for those who counted on him.I am reading what everyone is writing on here, and you all have valid points. But, I wanted to throw this question out there.
If Maddie (or any other woman) had truly committed to David to the point of marrying him and/or having a family with him, how do you think that would've changed him in terms of being a life partner?
By the end of S4 Maddie had to have known that. I think she more struggled with accepting that she wanted someone who didn’t fit into a predictable life. She knew David was capable of making a great life partner-one who could make someone incredibly happy, despite his more frustrating qualities. It is why she always got so jealous at the thought of him with someone else. She couldn’t fully decide on what she wanted her own life to look like, but she couldn’t really walk away either.