I find it quite funny and ironic that their API remains restricted because they don't want "low res pictures". Clearly they didn't realize what Android is.
Of course this is not the reason but it sounds good when you put it that way.
If given access to upload api would you make that api request with data that are usefull to instagram? Like what other apps are running in the background, contacts from the phone, gps location or other data that can be mined from the phone? Stating that you don't want to allow access because you want to keep up with quality of the photos makes me laugh. Once you apply a filter to the photo what quality are we talking about? Because that clearly is not an real life photo anymore.
Instagram being free for the user and making money is not about your photos anymore. Apply a filter to the photo and it's useless to them. So they need additional data about you to be able to make a profit. Likes on other people photos also won't tell much about you so cant be of much value for advertisement purposes. So for them the android platform is heaven with wp8 being more like a ****.
If you look at the permissions for the app in the google play you have a glimpse at what the real purpose of instagram is. And keep in mind that ios does not implement a permission list so some data from ios can be retrieved without you even knowing about that.
if wp8 was more open like android I'm sure that by now we would have an instagram on the platform.