Why do people think others are crazy for believing ghost?

I'm an avid believer since certain experiences as a kid and it wasn't just me seeing or hearing these spirits my mum my step dad my brothers all heard and seen the same things I saw now I'm asking is it possible that all of us are crazy or what? Because I've been called crazy for telling people about what we saw in these flats I grew up in. I'm finding it unlikely that all four of us are crazy if ghost don't exist how come we all saw heard and experienced the same stuff going on in that place?