Short verdict
Skip. Usually not worth luggage space, shipping cost, or the risk of buying before you know whether you need it.
Hair care is one of the easiest categories to overpack because large bottles feel like value in store.
What to know
Buy small treatment packs, travel sizes, or Korea-only sets if you have a specific reason.
What to avoid
Skip full-size shampoo and conditioner unless the product is hard to replace and you have luggage space.
Final verdict: small treatments can work; big bottles usually skip.