Why is the clutch there? Well for starters, in a way it helps regulate the speed of the car. Suppose you shift the gear to late or too early, pressing the clutch helps neutralize this problem. You might, of course now be tempted to press the clutch all the time while driving, but it is inadvisable to do so as you might ruin the clutch line. Pressing it for too long also consumes a lot of fuel, and hence, I would advise you to use the clutch only when necessary.