Jailbreaking iOS is quite a step for the majority of users, and means relinquishing the benefits and ease of the Store.
Arguably, if this article is any indication, elements of Win8 are not secure enough to outweigh the benefits of these quick and simple hacks.
Having said that, Win8 is less of a closed minimal mobile system, and probably better compared to OSX. Desktop with a tablet layer bolted on.
People who want to pirate WILL pirate. By creating the locked-down system on iOS, you force people who wish to change the feel of the dashboard to jailbreak their devices. They then install a couple Winterboard themes onto their device and at the same time, they come into contact with some nice games that they can tap a button to crack and install for free. This actually creates pirates by forcing them to become pirates to simply improve their device's theme.
Same for removing carrier bloatware on Android - people will root their device to remove bloatware. Once rooted, they can easily purchase games from the Android store, copy them out of secure storage, and then get a refund for the game while keeping the game. If the bloatware was removable by default, they would not have rooted in the first place.
Making it difficult to pirate by affecting your paying customers is a terrible idea - focus on customer value - pirates WILL pirate regardless. If you give out your game for free, pirates will still pirate it and you will still see it sitting on TPB (and others).
Piracy is an industry, not a customer. You can't sell to pirates by making it difficult for them.
It's to the point where hackers like Steffen Esser seem unwilling to release anything lest it be used for rampant piracy.
Possibly worse still, iOS apps can be easily pirated by exploiting Apple's developer tools. I imagine they will soon crack down on that, they must be aware of the amount of piracy that goes on.
What?
A jailbroken iOS user loses access to none of Apple's official application and music distribution channels.