During joint, textures get lost. Will apply only 1 texture. WHY?!

Why I am seeing the above and when I joint all the hair together, I see the image below?

I imported the hair as .obj and I can see clearly in my object lister and in my texture, that there is a lot of hair and has the correct texture applied.

During the joint process, why will be the reason of reducing/taking only 1 sample of texture and apply then to all the separated meshes?
Why are NOT the textures baked in a single texture as I see when I imported the .obj? When I import the .obj the textures are correctly displayed?

The textures most be baked (all of them) in a ONE single texture, and NOT bake only one texture to then apply to all of the objects/meshes with the chosen single-sample of texture.

The hair was made using different textures! That does not mean that display multiple texture and when thenI join the objects the software will choose one texture and then apply to all the hair.

For me this is a bug.

You can only join objects with the SAME textures.

Clone the hair - join - unwrap new UV and bake

Understood …
Thanks!