Some people worked very hard for their Dr./Ph.D, are proud of it an use it everywhere... "Hello, my name is Dr. FirstName Lastname". It becomes part of their public appearance and they expect to be called Dr. XYZ, not MR. XYZ, nothing wrong with that even though enough people don't care or see a reason.

Depending on your country of heritage/local culture it is more or less expected to use your academic title verywhere you go.

To some extend I can understand to use the Dr./Ph.D as that is a major achievement but specially in Germany, Austria,Switzerland a lot of people even always insits on having their old school academic titles liek "Dipl. Something", "Magister" or whatever to be present on all their papers...