I think he slicks it back for big occasions, and that's kind of how I see him when it's like that...like, this is Jack making an effort, or dressed up.
Hairband Jack is a little more casual. Neat and tidy but practical, low maintenance.
But sometimes even with the hairband it gets a little untidy, and we can allow that too:
And without the hairband we get a nice effortlessly dishevelled look:
Like most on here, I prefer his hair dark, with fewer highlights. But when he really committed to the blond, I'm not going to lie, this worked for him:
Also, braid Jack. I love braid Jack. I would marry braid Jack and spend the rest of my life doing his braid for him.
Long story short, Jack's hair is glorious.