In TNG, Picard did have pretty much full control to the Enterprise-D from his captain's chair. In "Encounter At Farpoint," it was said the armrests on his command chair featured access to the main computer, backup helm & ops controls, as well as controls for shields and weapons. In an emergency, Picard could probably run the entire ship by himself from the captain's chair, but it likely was considered an option of ultimate (last man standing) resort, IMO. Otherwise, it might have been considered more effective to have dedicated control stations for each system, allowing the captain to concentrate on making command decisions.