What makes you think so? How do you know how many exploits people are sitting on, but not using because they don't have a good sandbox escape exploit? Well, no

What makes you think so? How do you know how many exploits people are sitting on, but not using because they don't have a good sandbox escape exploit? Well, now they do have an escape. That useless IE/Chrome exploit might be able to suddenly gain SYSTEM privileges. You can get compromised by such attacks no matter how responsible you are.