You do?
Well, there are things happening whether you are logged-in or not, right? These things are events being run on a computer server at wherever Inno has its data centre.
When you are logged in, Flash (the software the game runs on, inside a browser) is asked to talk with the server and the server can talk back to it. This is how the neighbourhood knows the current state of the Casino Wheel: when another player spins the wheel and wins a prize, the server, knowing you are online, sends information to Flash (which sends it to the FoE game running on your browser) to let you know the current status of the Wheel.
Some things are obviously not being communicated from server to Flash. This might be because the FoE program is botched, it might be that Flash doesn't always pick up the notification that gets sent to it (e.g. a glitch in comms, or you switching to another browser window can do this) or it might be that with all the timers going on, Flash sometimes doesn't clear memory very well (a long-standing problem: every new minor release clears up some memory leak but seems to add a new one of its own).
So, the only way to be sure that you have all the up-to-the-minute data, is to cause a complete refresh of the game.
As an aside, this might also make it clear why it would be helpful if all players logged out of the game when they aren't playing it for 10 minutes or more.