There's definitely cases where a distributed database will have higher bandwidth than a single-node database. Since each range is replicated across 3 machines, that means if you have a lot more nodes than 3, the overlap of ranges significantly decreases and you start being able to handle more requests than a single node can.

However, the latency will typically be higher since it always has to talk to at least 3 nodes.

If you consider CRDB's DistSQL which lets you run queries on multiple machines, it might be possible to beat a traditional RDBMS on read latency for large queries.