Two possibilities :
- Other Company
If I have fiber and switch to cable (or vice versa), the cable company will remove the fiber from my house but they will leave it at the pole because it is the other company's property. Or they may let the other company...
- Save for the next customer
If I move out, the company might disconnect but leave at the pole because of the next tenant or owner wants similar service then they can use the existing cable and save $.
But in any case, as stated by Harper: if the wires are near the ground, don't touch. Call the electric utility (they normally own the pole) and they'll check it out and remove, repair or notify another utility as needed. Even if a cable really is low voltage "nothing", things can get messed up at the top and make it hot. One time I had a low hanging coax situation. Called Pepco and they took care of it even though I knew it was comcast and knew that 99% certain I could have climbed on a ladder and done it myself. The 1% risk is a serious one.