A lot of people run the larger furnaces year round, hence the need for insulation. You obviously don't want it pumping heat into the basement in the summer.
You still get some amount of heat in the winter even with the insulation. You could just take a panels off if you wanted, it won't have that finished look though.
If you have a hot water jacket that more than offsets the cost, plus it will add many years to the lifetime of the unit.