You don't "have" to. But if you're flying in/out of the US, the TSA may break your suitcase open to inspect the contents if you send it through locked. And you won't get any compensation for any damages.
Yes, it is not recommended to pack power banks in checked luggage due to safety regulations.
Yes, HOWEVER- if it is locked, and TSA needs to inspect the inside of the luggage, they CAN break it open. You should leave it unlocked.
Yes, you can carry a smartwatch in your checked luggage.
Yes, you can carry a watch in your checked luggage.
Yes, you can pack deodorant in your checked luggage.
Yes, you can pack shampoo in your checked luggage.
No, aerosol sunscreen should be packed in your carry-on luggage, not in your checked luggage.
Yes, deodorant can be packed in checked luggage when traveling.
Yes, you can bring shampoo in your checked luggage when traveling.
Yes, hold luggage and checked luggage are the same thing. They refer to bags or suitcases that are checked in at the airport and stored in the cargo hold of the airplane during a flight.
Yes, you can leave the airport after checking in, unless you have checked luggage that needs to be dropped off or you are required to go through security.
Yes, you can bring a Swiss Army knife in your checked luggage, but not in your carry-on luggage.