The chopper's business is to provide road and rail transfers hence why this service has lasted for so long, along with providing 'awaydays' for the islanders to go shopping, hairdressers etc. etc. etc. in a mainland town, until now Penzance.
Between PZE and the Scillies there is no rail, insignificant roads and the only airfield is owned/operated by the chopper's competitor.
I stand to be corrected but I don't think Truro is a licensed airfield.
And why the hell would they build a new heliport facility, free landing/navigation fees, free parking, their own hangar etc, only to position, at great expense, the choppers to/from NQY every night?