We always shout 'Bless you' when someone sneezes.
When you think about it, it actually makes no sense to wish someone health if they are not sick. But: if you don't shout it, it is also uncomfortable. A kind of sweet tradition that is being maintained. We just say it without thinking about it.
I like the situation when someone sneeze in a full & silent bus or train, and one person is yelling 'bless you!' Social contact on public transport seems to be dying out, except in the case of a sneeze.