Well, not knowing what you're looking at, it's hard to say.
I'm assuming when you say hole, you just mean a hole + pads in the circuit board, not a female connector.
One reason you'll see multiple grounds is that everything connected to the board is going to need it's own ground wire. Typically, for hopefully obvious reasons, designers locate all the pins going to a specific connected device near eachother, usually in a row for some kind of connector (though cheap boards often just solder wires directly on).
as for unused points of connection, the cost of having PCB's fabbed is a function of the number of boards of a given design you're making, the size of the board, and the parameters (coating, how tight a tolerance you need, what substrate, etc) you want on it. Thus, if you're going to be making a bunch of similar things (say, a bunch of different toy cars with different assortments of lights or whatever), it's cheaper to just make one board that can handle the fanciest one you plan to sell, and use that in all the models, with some of the connections unused.