I would think that's definitely true. He's got a very nice, comfortable life with her, but they don't really have much in common (other than mutual greed and laziness!). Alfie likes to go out, travel, drink, do things that are (slightly) adventurous. Zoe doesn't like any of that. And yes he can go out with his friends, but it's not really what you would picture as a recipe for happiness if you were thinking of committing to lifelong relationship. I'm sure he looks with envy at couples like Lotty and Zac who actually do things together.He’s said before he hates committing to stuff, even something he wants to do like buying tickets to a show just incase something better comes up that he wants to do... maybe he thinks the same with Zoe? Scared to make that commitment incase someone better comes along?
And by being with her from so young, he's never had a chance to grow up and experience independent adult life - he's always been with her. It's not as if he's got it out of his system and is ready to settle down.
I think he's keeping his options open and hoping something better might come along, but he's too scared to cut the cord - knowing how much more (financially) she brings to the relationship.