It's in the name - HBM increases bandwidth. It does reduce latency a bit (since the electrical path is shorter), but the bigger and more fundamental latencies (

It's in the name - HBM increases bandwidth. It does reduce latency a bit (since the electrical path is shorter), but the bigger and more fundamental latencies (row and columns) have not changed in many many years and are unlikely to. (It'd be possible to make them lower by proportionally higher power use and lower density, a trade-off which no one seems to be willing to make).