maybe it’s just because that’s the more memorable/unique parts of their name?
trump/biden is much more distinctive than donald/joe
clinton could refer to both bill or hillary
obama/kamala is more memorable than barack/harris (though maybe for obama that’s just because I’ve heard ‘obama’ so many times)
I’m not saying that’s definitely not true, just that there might be other reasons why
you all need to learn to distinguish between the people/the government/the country