Because Apple is so secure. Just ask the Fanbois. Apple loses copyright battle against security start-up Corellium - The Washington Post
A federal judge in Florida threw out Apple’s claims that Corellium had violated copyright law with its software, which helps security researchers find bugs and security holes on Apple’s products.
Earlier this year, after the hackers were locked down for a couple of months and bored to action, Zerodium, one of the big Zero-day, cleraing houses, stopped paying for any Apple iOS hacks. The market was saturated. They didn't feel the need to add to their collection of ways to bypass Apple security.‡
So anyway, the judge dismissed Apple's suit saying that Corellium's use of Apple's stuff falls under "fair use."
‡ and in the early part of the year, a lot of those issues revolved around iMessage. All the bad guy had to do was send you a malicious message. You didn't have to open it, or click on anything, and they owned your iPhone. Yeah. Security. Though rumor has it that Version 14 of iOS is more secure. Time will tell.