Comment by cosmic_cheese

In theory. In practice, a lot of EVs (and hybrids, which could do the same thing to a more limited extent) ship with the same cheap flooded lead acid 12v batteries that ship with ICE cars and don't handle constant charging/discharging well.

This puts a cap on how much the "smart" systems can do because it dramatically increases cycle count and thus the risk of the 12v battery losing the ability to produce enough voltage to start the car, leaving the driver marooned somewhere.

It could also result in a noticeable "vampire" drain on the high voltage battery which looks bad and could put you at a disadvantage vs. competitors.