I don't think this has anything to do with helicopters as you can get 'fixed wing headsets' with scaffolding as well. A lot of the time they tend to be the cheaper, older headsets as most manufacturers seem to prefer bendy ones nowadays. The only difference, normally, between a helicopter and fixed wing headset is the connector plug(s). A lot of helicopters seem to have the single plug, instead of the typical two plugs of fixed wing but this is not always the case and, of course, you can buy converters.
I think the area where the scaffolding comes into use is if you want to fit a microphone to a helmet. I this case the scaffolding affords you more flexibility on the distance you can move the boom in and out and allow better positioning of the microphone. With no evidence other than what I've seen, I would suggest helicopter pilots are more likely to be wearing helmets than fixed wing......well, certainly where I live and they insist on using them for cattle mustering (a fantastic spectator sport)