Why is high-end curly hair often different quality from straight or body wave?

High-end hair was cut directly from a donor, thus all cuticles are aligned and intact.

However when you start curling the hair, the direction of the hair is in 360 degrees, and no longer in one direction. Hair without aligned cuticles will tangle, so will curled high-end hair.

The tighter the curl, the worse it gets.

A specific amount of the cuticles has to be removed to prevent this tangle.

It's done in acid, so curled hair is mostly going to be lower quality than straight hair from the same line.

It's important to get the amount right, and a lot of vendors remove too much.

However, when done well, the high quality hair with some of the cuticles removed is still higher quality than the middle-end hair (remy machine aligned hair)

The same thing happens to frontals and closures.

The hair is attached to a closure, on one end will have roughly 4 inches sticking out, and on the other end the full length of the hair.

Some of the cuticle will get removed, as these two ends are both on opposite directions.