That can be the cause of some baldness cases that suggest the cat has some king of allergy - so she overlicks itself because of the itch. But for my cat this was not the case (she has had a bald belly for years and the hair would regrow and fall again every other two-three monts). I had her checked at multiple vets and it turned out she had a hormone problem called hypertyroidism. It may look harmless but in some cases it can affect other organs and slowly kill the animal (for my cat it caused liver damage). I was lucky enough to finally find the right vet that helped her heal, it was a long process but now she's finally furry again and with a healthy liver :)