Its interesting that 50% of the replies here use the word "technique"... I believe, and teach my students, that you are not practicing to learn a technique, rather a construct.
The linked article makes a good point that the vast majority of us will never have to face a combat situation (unless you are unlucky or you work in law enforcement, the military or in the health system), it is more likely to be someone you know. Being brutally honest, how many people do you know personally and that you come into regular contact with are proficient or professional fighters?
There can never be a comparison of down and dirty fighting, the kind where you've lost your weapon and you are biting, gouging and clawing at your enemy, and what we practice in the dojo, but is that really the point?
Lesson plan 1: someone tries to attack you with a knife or some other bladed instrument. a) Not be there in the first place b) Try and talk your way out of the situation c) Run and a distant d) Try and deal with the attack.
I would hope that by practicing our "techniques" we stand a (slightly) better chance of dealing with an attack that not having trained in recognising the patterns and shapes that these techniques encompass.
Lynn's post was right on the money:
Very different intensity and intent.
We don't generally practice or prepare for combat because we won't usually encounter it.
As with all things in life though, YMMV...