Every race in the universe has its own kinds of greetings, and the Doctor doesn’t merely mean in terms of different languages.
On some worlds, the proper greeting involves spitting in each other’s face, while on others, rubbing buttocks is the height of good manners.
Delviunx Eight, for instance, has elaborate dances for everything from inviting guests into your home, to saying hello to family members, friends, or strangers on the street. The Doctor does his best not to cause offence, but he’s slightly hampered by only having one pair of arms.
Thankfully the natives make allowances for such deficiencies.