Yes, I've seen some clearer cases made for networking. In networking there is no standard for the hardware interface. Every vendor does their own thing. Except many can at least handle virtqueues carrying virtio-net messages for the data path, so some framework like vDPA may make sense (I'd prefer to see a full NIC interface standard emerge instead).

In storage, however, the industry has agreed on NVMe. This is a full standard for control and data plane. All storage products on the market, including DPUs and SmartNICs, just present NVMe devices. So there's no case to be made for vDPA at all. It just isn't necessary.