No I'm not confusing simplicity with ease of use, I'm referring to the simplicity from the users perspective (i.e. what matters most) which is the conceptual and cognitive overhead required for them to know to accomplish what they want to do. In the same way a GUI Desktop is simpler and more comfortable to use for most people than DOS or a single Google search box or voice input are simple enough for anyone to use despite the complexity they encapsulate.
Apple starts from the user experience first and works their way back to the technology. Technology is just an obstacle in order for them to be able to accomplish their desired experiences, it's not something they put front-and-center or use it to limit or influence how and what features are implemented.
Kids can use an iPad without ever needing to know what a File System is, there is no impedance mismatch to them, they're not spending their time thinking about how their multi-layered video that just created is physically stored and synced. They just use an App for a while, switch to other apps, then re-open their app when they want to continue working on it.
Exposing internals like file-system layout means the OS is no longer managing the files, they need to cater for manipulations whilst still supporting transparent cloud backups and syncing, they need to design a completely different UI for power users with lots of features all working with multi-touch yet still have the features power users expect from a Desktop OS, e.g. downloads to be in a central "Downloads" folder instead of being grouped and isolated in the App that downloaded them.
You've at least acknowledged you're not the iPad's primary audience but labelling it as just a toy means you've still failed to realize its appeal. Smart Phones and tablets are becoming the primary computing platform because they empower users to be able to do more, Apps are optimized around use-cases and tasks making them much easier and more enjoyable to use than Desktop software.
I have a lot of anecdotal evidence on how the iPad is the only computing device my parents have ever enjoyed, how after so many years they still can't conceptualize how files and folders are structured, where their documents are saved, how full-screen windows and pop dialogs makes them think their PC is broken.
Even myself as a power user I find lots of apps that are much better on an iPad, inc. more advanced tasks like browsing and comparing real-estate is so much faster and effortless. There's also tasks that you just can't do on a PC or are frustrating enough that you wouldn't bother with, e.g. Making phone or video calls, taking and sending photos, Live Directions and Traffic, paying for coffee, even core tasks like browsing photos, Facebook or the Internet are generally more enjoyable on an iPad.
But ultimately anecdotal evidence is useless as everyone can provide their own to contradict them, the best indicator we have to go with is Sales and by this measure Apple's recent iOS strategy is a lot more fruitful then their decades old Desktop OS strategy - they have no reason to make iPad's more like OSX - they're reaching and empowering more people then they ever have, they're making the technology a transparent implementation detail so much so that iPads are often referred to as a magical pieces of glass.