Simple jokes are almost always voted down. Even when they're funny, they're not the target tone of the site. It's not personal, it's just an editorial and community-direction choice.
I had noticed everyone had the same typical serious programmer personality here. That's why I enjoy reddit a lot more because it's not like that 100% of the time.
don't forget these startup guys are literally saving the world one webapp at a time. It's serious stuff.