Why?

[smurfchops]

Why do some people wear a mask under their chin, or over their mouth and not their nose??

[bookbinder]

They're putting on a pretence of doing the job properly, but they're too lazy to do so.

[andy-hughes]

Under the chin so it's ready when they want to put it on.

Under the nose - because they find it uncomfortable but want to be seen to be making the effort.

[jno]

want to be seen to be making the effort

except they're not ... the effort required is actually that last inch up over their nose.

Under their chin - could they be bearded ladies?

[douglas9401]

They are dolts, contrary or contrary dolts.

[burlyshirley]

It depends where they are, if outside probably under the chin until they enter a shop, when they pull it up !

[Redhelen72]

Coz they are idiots!
Several people on the plane yesterday tried to tell the hostess that they were wearing a mask!
She told them very politely that they were not and to put them properly

[tiggerblue10]

Like BS says, I put mine under my chin and pull the top bit over my nose before I go into a building or bus, train etc.