Why the 'Headwear'(or 'Hat') does not show up on the custom Human's skin?

I wanted to apply skin that shows up the ‘Headwear’ on the Human(org.spongepowered.api.entity.living) since last week and four days.

i) Use SkinData with UUID
–> Success, But the result was like the title.

ii) Depends on SpongeCommon, and use MixinEntityHuman
–> Fail, It occurs the exception of NoClassDefError(?) every time.
So I gave up of the second one.

iii) Depends on SpongeCommon, and use EntityHuman
–> Success, I didn’t realize that EntityHuman and Human are castable to each other.
I (forcibly?) got the GameProfile privately assigned as name ‘fakeProfile’ in EntityHuman with Java’s Reflection and apply Skin’s texture and signature to the profile.
But the result was same as the first one.

Why skin’s headwear is not showing up?