Is that really what they're worried about though or do they just want to be in control? That's how it seems.
Does it even matter? Android has huge problems with malware. That's the price you pay for having such an open OS. Not only that, but jailbreaking allows you to install pirated apps. I know that's not the main reason for jailbreaking for many people, but it's a reason that Apple would want to make jailbreaking as difficult as possible nonetheless.