Ultimately it comes down to this: Tim Cook has money in the bank, right now, billions and billions of dollars that, even if he WERE to face the heaviest repercussion anyone can face for being openly gay in the workforce in 29 states of the US (termination), is just sitting there. Apple doesn't own it - it's all his payroll. He's literally set for life, and probably has been for a majority of his tenure as CEO. I do not have this luxury. I don't have a bank account (due in part to the large amount of debt I already owe staring me in the face), and I live paycheck to paltry paycheck, indefinitely. When framed this way, I think one would be very, very hard pressed to tell me Tim Cook coming out at work and me coming out at work is at all even remotely the same damn thing with similar or, lord, more things at stake for him!
The goal is humanizing gay people. That's the importance of coming out. You need to come out to people you can trust and people whose opinions you can change and you as a tiny, unimportant person probably need to be careful. At this point Tim Cook coming out isn't very important or brave. Ellen Page, maybe, because she's not a very stereotypical lesbian and is even a bit wholesome, girl next door. The Cook story just shows that it's less and less of a big deal every time this happens with a public figure. Every time some random person comes out it could be 1000 times braver, and even more important, than a celebrity, it's just not news. There's no angle for public interest or spectacle and there doesn't need to be for little courageous acts to be important.