My bike has an aftermarket exhaust on it as well. I think I strike the balance between being loud enough to be heard when filtering / in built up areas (especially if I knock it down a gear) and being antisocial. When you open the throttle on mine there's an amazing whine noise which I love and I suspect that would be present on an electric bike. You'd lose a lot of the drama / fun and also I feel that for filtering it would be potentially dangerous. Have you seen the electric Dominoes scooters? They have speakers on which goes "Dominos Dominos Dominos Dominos" repeatedly, kind of mocking a Lambretta rhythm.... Utterly bonkers.
Also, there's nothing quite like someone who is on their phone and weaving all over the road having their conversation interrupted by a motorcycle in first gear riding alongside them. I feel electric bikes will need some kind of EMP or other mechanism to allow revenge on arseholes who put our lives at risk.
EDIT: Me and a friend who both ride as our primary means of transport did an analysis of an electric bike's costs and found it to be pretty much break even. The killer was two fold - one that longer journeys on it would be just not doable and that the servicing / dealer network just isn't there. Plus you can't really get a small garage to do it as the tech is pretty proprietary so you can get raped for service costs.