you asked in your tags if it's "too Lucius".
Lucius used to ridicule Draco for his unruly wavy hair.
"What kind of hair is this? This is not the hair of a Malfoy!"
No, it's not. It's the hair of a Black.
Draco inherited the Malfoy hair colour, but the Black hair texture. And all through his childhood and teenage years, Draco straightened his short hair every morning, and after every shower, every Quidditch practice, every walk in the rain where he wasn't fast enough with a protection spell.
All while Pottah couldn't care less that his bird's nest of a hair was developping a mind of its own...
The fact that the Malfoy heir had to have straight hair was ingrained in Draco just as much as the fact that the Malfoys were part of the sacred 28 and that Draco would marry a nice docile, blond, pureblood witch one day and have at least one nice docile, blond, male offspring one day to continue the Malfoy bloodline.
Fast forward to now, though, and a lot has changed since the war ended.
Draco is no longer listening to his father. No, thank you! Draco is married now, to Pottah Harry no less (But, Draco, he's a halfblood! He's- he's a man!!). And Draco is happy!
And so Draco experiments one day, tries a spell to see what he would look like with long hair. He wants to know if growing it out would be worth the trouble. And Circe, he loves it! And Harry loves it, too!
But Lucius, oh, Lucius...
Lucius is green with envy because he knows his own hair will never look as lucious and voluminous as Draco's. No spell or tincture or potion could create this beautiful horrendous natural flow.
And Draco knows it, too. Draco knows that his father is jealous; he knows now that his father had been jealous all along.
And so Draco holds his head high, long wavy hair and all, secure in the knowledge that his father won't get to belittle him anymore about things Draco had no control over, secure in the fact that his husband Harry loves him -- just as he is. Wavy hair and all.