The hotel provides free shampoo. Can this be regarded as illegal income?

Not exactly. The hotel provides free shampoo. According to relevant laws and regulations, guests can take away the toiletries provided by the hotel. Small daily necessities such as shampoo and shower gel are not valuables of the hotel, so the degree of freedom is relatively high. Moreover, the hotel can also provide free or charged small daily necessities for guests to take away. However, if some valuable or easily damaged items, such as perfume, bathrobe, bedding, etc. Don't take it away at will. So it's not illegal income.