Tapes are great for true cold storage (will easily last many decades!) but they will wear out significantly with more intense use: you only get a couple hundred passes total over their full data capacity, either read or write. In practice, you still need plenty of big hard disks to act as nearline storage for practical use, and the tape only rarely does storage and retrieval in bulk. This is also why you see mechanical tape libraries with tens or hundreds of tapes for a single read/write unit: you don't really need more than that.