Hotel responsible for register at local police station ?

"After leaving the airport, remember to register at local police station within 24 hours of arrival if one wants to stay over 24 hours. Those who live with family or friends need to go to register in person at the police station with relatives or friends. Those who live in hotels do not need to go, because the hotels will do it for the guests."
Is it the Hotel's responsibility or the traveler responsibility ? Is the hotel doing it just as a courtesy service ? In my last trip, I used the 144 hr option at Shanghai. I had to go to the police station with the hotel manager on the 4th day. I don't understand Mandarin. But was told that we had to pay penalty for not register. The Hotel wants us to pay half of it.