> How would you feel is someone was walking on busy car parking and checking if doors of the cars are open? It' what port scanning is, checking if the car has open door.

More like sending a "hi, can I enter?" signal to a self-driving taxi that has been left waiting in a public arena.

Don't put a server online with a public IP if you don't want to receive those signals. Don't send "hi yes you can enter!" responses when you get the query, if you don't want to let people in.