They don't??
Every one I ever seen operated exactly the same way - clutch pedal up = clutch engaged - clutch pedal down = clutch disengaged - if it doesn't work that way - IT'S BROKEN.
Exactly where along the pedal travel it engages/disengages may be different - even on identical make & model vehicles, and should not be considered a problem - a Grand Vitara for example has a self adjusting hydaulic clutch, but, as the clutch nears the end of it's life, you'll notice the engagement point getting lower & lower, until you only have to think about releasing it, and that involuntary "muscle twitch" in your left leg that occurs with the thought will start the car rolling.
When the clutch is worn to this stage - you'll find that it drags - and selecting first becomes a struggle, and reverse will grind - and you can release it, and push it back in - as many times as you want - it will still baulk going into first, and grind going into reverse (it's the synchromesh that lets you get into first without grinding - but reverse is straight cut, and no syncromesh ...
