When we're out to eat, we're there to relax and take in some delicious food and lovely atmosphere. If we're with others, then we're hopefully enjoying their company as well, but we're mainly there because we're hungry.
Most restaurants don't give you much of a look at what's happening in the kitchen, so your main point of contact is your server. And the longer they've been doing their jobs, the more they've learned while ensuring you have the smoothest experience possible.
However, it's not always obvious exactly how they do this, nor is it clear when a small habit of theirs might have an alternate reason behind it.
But nothing can stay a secret forever and some servers have let the internet know what little tricks they often use to keep you coming back.