Most of us(or all of us) press clutch while changing the gears during upshifting because we are told to do so. But except first gear, you can upshift the gears without using the clutch.
During upshifting, your bike starts to accelerate, so after some interval, you have to change the gears for smooth running. So while accelerating, you can upshift without a clutch.
But while downshifting, the vehicle is decelerating so you need to remove your driving and driven member to shift gears. That’s the function of a clutch.
Go ahead, try now.