Exactly. But plenty of people claim they don't need it, or that their moves are "too deadly" to spar with. So they fill up their time with one-step moves and defense "techniques". Then I get pissed and argue for 5 pages about it.
The thing is with most moves you can't spar full contact or the sparring will last about a couple of minutes, then someone would have something broken. In that instance what you do is get a couple of higher ranking belts and do full speed drills like I mentioned.
One person is the attacker and the other the defender. The attacker attacks once and the defender has to do something anything, if he doesn't or gets hit or whatever that round is over and either it's the other guys turn or another try.
The defender capitulates and gives appropriate reactions to hits. That is hit in the groin and you keel over a bit. Moves that involve joint locks can be used more forcefully to force the attacker into the appropriate position.
Sparring, for standup martial arts, basically amounts to light to heavy contact kickboxing and is not an end all for defense. You really can't use anything that would work really good in stand up because your parnter WOULD get hurt.
Keep in mind I'm not talking tkd sport rules here.
For instance, most of my favorite moves in kenpo involve stepping on the back of the opponents knee, taking it all the way to the ground (slamming it in fact) then from behind grabbing the chin and breaking the kneck.
While I can slip behind someone and just tag the back of their knee. If I was to follow through in a sparring situation it's not likely I'd be able to control my opponents fall enough to keep him from hurting his kneecap, and then slamming his own face into the floor.
so, although the above cop out is used by lots of instrutors, in some cases it is valid.
But, this is where full speed one step sparring comes in. For students with more rank/control, they can pair off and do continuous.
All that said..... what I've noticed is a lot of people have never been in a fight where there is real potential to be hurt and have fantasies or misconceptions on how it is.
Most people think they are going to pop some guy once in the groin or throat or whatever, and he's going to keel over.
They don't account for adrenaline reactions or just plain being willing to really go full out. And most can't even identify how fights start so that they can either avoid them or just know to be ready. (Though I prefer premptive myself)