The question of why Allah has established His law in this way is not something we can answer. Only He knows the reason for it. Yet, He has provided provisions by which everyone would be protected, like you mentioned, a woman can take agency to divorce herself. Unfortunately, most people don’t know about these rights or they don’t consider including them in their marriage contract. As far as abuse is concerned, no one should live with it or tolerate it, and Islam has a strict policy against it. Once again, it is likely poor human implementation that does not protect the woman.