I always remember those good-shampoo-bottle hotels fondly when using the old bottles with the hotel name on — maybe a missed marketing opportunity, "travel well with X hotel, please reuse me".
malmaison (UK Hotel chain of mostly 'boutique' type hotels)actively encourage people to nick their shampoo, and it's actually really good stuff too! https://www.thesun.co.uk/news/3380603/psoriasis-cured-hotel-free-shampoo/amp/