That would make great sense, if there was a way for technical users to opt out of the walled garden. But it's the very opposite -- Apple spends a lot of time and money making it harder to jailbreak the phone, in ways that have nothing to do with defending against malware. If they do their best to make it impossible to opt out, then it's not about protecting your safety. It's about protecting the business model.
There's an argument for protecting the business model, of course -- making jailbreaking more difficult also makes piracy more difficult. The App Store has funneled a ton of money to developers, which in turn makes for better apps for everyone. But the notion that Apple has gone to absurd lengths to prevent jailbreaking because ... "We [developers] gave these freedoms away by using our talents to cheat and scam our customers"? No. That's not how freedom works. This is about money, plain and simple.