Let's say for a second it was accurate (It's probably not), perhaps it's because Android has a far higher market share globally, and it's much cheaper and easier to get started writing apps (or malware) for Android than say iOS.
You also don't need to buy a single device from Google to get started. You can take the PC you're at and get started right away, and publish that app (or malware) without spending a penny (though I don't recall whether they still charge that nominal fee to get a developer account).
Saying 90% of people root for piracy is hilarious, I rooted every Android device I owned until the last one or two, and I've never pirated anything, why did I root? Mainly for customisation and host-based ad-blocking.
I can't understand the thought process of these people who think the things you own should be locked down to protect you.
We should stop selling screwdrivers too in case someone's granny tries to open their toaster and electrocutes themselves, after all, a screwdriver is the pre-tech root access to all things electrical and electronic. I suspect those same people who argue in favour of locking these devices down would also say "don't by silly, my granny wouldn't open her toaster with a screwdriver, because she's not an engineer".