Only around 5% of the hours flown for most multi IFR guys are logged as actual. This is typical for pilots who have a cold winter season to deal with. So if you fly 500 hours a year, realistically on average you can expect 25 hours of instrument time. The cost and complexity of operating a dual pilot modern twin helo don't really make much sense when you consider the capabilities of the aircraft that you're just not utilizing most of the time. So skills can get rusty, both cognitive and dexterous.