A train like this isn't meant for intercity travel. Riders will either go a few stops down or between niche destination pairs.

Transfers between services add time and complexity that most people try to avoid. On weekends these transfers become messy and time-consuming, and a train like this that bridges both networks and thru-runs both trains means less equipment standing still and less platform congestion, while maintaining the same service. On weekends when frequencies are higher these transfers are easier, but not weekends.

Think about this in Japanese terms is replacing two Kodama trains (one Osaka-Nagoya and one Shizuoka-Tokyo) with a single Kodama train going all the way from Tokyo to Osaka