Actually saying things after one sneezes varies according to nation.
In some countries they say it because in the past (from aprox. XVII), people sniffed tobacco for their pleasure and they sneezed big time, also they often offered it to one another, so they were saying "cheers" like when we drink together. In other places like Spain they say "Jesus" or "health", because when there was a horrible ephydemia, one of the signs of having it was sneezing, so they were like "praying" for that person.
In Asian countries it's inappropriate to even blow one's nose in public, you have to go to the washroom or a seculed place to do it. So sneezing - as it's closely related - has no reaction from the surrounding people. It's considered dirty, so it's not that welcomed.
(But for example, slurping while eating and giving out noises are signs of satisfaction, also they talk a lot during meals with one another. In Hungary for example it's really rude, and we're also tought not to talk while we eat [no-one is interested in what's in your mouth, and you can easily choke])
Customs are customs.