A simple example of why functional training is more effective for you.
Most people sit when they do overhead presses. Leaning against the back of the seat. This is NEVER how you would lift something overhead in every day life. So why train that way? In real life you’ll be placing something on a high shelf. So train for real life. Stand when you press! It will engage more muscles, stablizing your core and strengthening you for when you have to lift a heavy object and place it.
Functional training for everyday life will keep you fit and help you prevent injuries.