(Assuming you are talking about a corded desk phone.) This is not the reason for the weights. Remove them from the base, and the phone ceases to stay put when

(Assuming you are talking about a corded desk phone.) This is not the reason for the weights. Remove them from the base, and the phone ceases to stay put when you pick up the receiver (which is attached by a springy cord). Remove them from the receiver, and it is not heavy enough to keep the buttons on the hook depressed when hung up. (Source: I did exactly this in college, with exactly these results.)