An individual strikeout doesn't mean that much. A pitcher would be just as happy with a popout, a weak liner or an at-em grounder in the same situation.
the need for a good K rate increases in one out reliever situations more than in over the span of the game situations.
Leading to everyone longing for Gagne type of monsters.
The starting pitcher is assigned 9 innings every 5 days to procure 27 outs, 3 at a time. Back in the day when you had 3-4 starters a team the pitching load was shouldered by less players and "spreading the wealth" in aquiring outs was prefered, because the ball was deader. As the ball livened pitchers pitched lesser innings, were expected to be stronger to combat the increased hitting by keeping the ball out of play more.
The hitter will get 3 ab's in the game for sure, everyday if he's a starter if he K's then he's going to get another chance later in the game, the next day, the next week. And if he accumulates bases then he is evening it out.
The pitcher on the other hand appears only two times a week and helps his team more by limiteding the ball from being in play.