The other day I described myself to a coworker as having knitting ADD. She was asking what had happened with some socks she had seen me work on on a previous day and when I told her they were at home waiting to be knit on again she just shook her head and laughed. It seems that having multiple works in progress is something that is frowned upon by your average non-knitter. Just like having extra yarn is seen as obsession rather than preparation.
But here's the thing. If you're privileged enough to be in a first world country, then you probably have more of a lot of things than you can use at one time. You have extra food that you don't plan to eat all at once (and probably several things of leftovers that are arguably meals in progress). You might own movies, which you really can't watch all at one time. You even own more clothes than you can reasonably wear at one time. So why should I not have more projects than I can knit at one time. After all, this is a leisure activity, so I should do what I want if I have the resources. It's not ADD, it's getting the maximum enjoyment out of my sticks and string.
At least this is what I tell myself as I cast on another sweater.