I've noticed that many members here have chickens. In my community, if people raise anything they're most likely to raise chickens. Do you see chickens as the gateway livestock? Did you start with chickens?
I think lots of people start with chickens because they're relatively easy to care for. Plus, some people don't feel comfortable raising livestock for slaughter which makes chickens a good choice since they provide eggs for years before heading to the stew pot. Other than dairy cows, goats, ducks, and horses, most other livestock are raised solely for their meat and hide.
Chickens were the first livestock we raised. We 'inherited' a small flock of laying hens when we bought our farm in 2000. The next summer we raised a couple batches of meat birds. They are relatively easy to care for (we day-range our meat chickens and turkeys, snow-free months only),and offer quick in and out. We've kept laying hens and meat birds ever since.
I'd agree that chickens are really easy to raise, even kids can do it. In fact that's the first livestock I raised when they brought eggs and an incubator into our first grade class at school. Since then I've raised dozens of flocks, all different breeds.
They were my starter birds. Chickens have personality and raising them is a rewarding experience because they gift you with eggs so often. It made me feel competent enough to raise other fowl.