There may be some trade off between battery size and weight. Although, as noted, the Oregon batteries have significantly increased capacity without doing this.I'd think the batteries add a lot of weight. Notice the 11.2lb. makita.
The Makita with the 36V battery is listed as 10 pounds; 11.2 lbs is with two 18V batteries and the adaptor, for those guys who have already invested in those batteries for Makita contractor tools.
Philbert