some of them are. I'm typing this on a keyboard with browns in an open plan office, and the three people who sit within two feet of me have no issue with it.
I work in an open office with 5 other programmers around, and none of us are bothered by each other's mechanical keyboards. We have a mix of Cherry Blues and Browns. We all agree that it's the least annoying thing about our open office.
It's a shared cultural thing unique to each company, no need to cast a blanket statement.
Blue and green switches are inappropriate for a shared office, but if you get brown switches and install sound dampeners then they can be as quiet as a normal keyboard.