Why do some people turn off preview messages in lockscreen on iphone?

Why do some people turn off preview messages in lockscreen on iphone? - 1

Added (1). who would they want to hide the messages from?

Because it is private and they may not want other people to see their messages.
Edit: It depends, they may have very nosy parents, friends or they just don't want random people reading their messages. They could be texting about sensitive information that shouldn't be viewed by everyone. We don't know why exactly this person is turning off the previews, if you want a define answer, you should ask them.

Cuz of privacy

I have mine off. Don't assume you know everything.

Some people are just private.