My friend Shaine kept his viva secret. In his final year he got married, wrote up his thesis, applied for and got a place on a teaching course, prepared for it, submitted his thesis and then prepared for the viva. He had a lot going on, and I guess he didn’t want people asking after one more thing. We only found out after he had passed.
It worked for him. Most people won’t keep the viva a total surprise from their friends, but I can understand why they might. As with many things, there are pros and cons. What will work for you? Think it through: do you want the help your friends could give, or the space that might help you to think? There’s no right or wrong. Think about what you need and do what will help you most.