What good can come out of a K?:
(1) if no one is on 1st, the C can drop strike 3 and you can get on base;
(2) you prevent yourself from hitting into a double or triple play; and
(3) you (or one of your teamates) don't get hurt running the bases when the ball is hit.
And that is about it.
Sure, after the fact you can say a groundout is an out just like a K is an out. But how many good things can come from putting the ball in play and still making an out? Alot more good things than when you K.