Over the last two seasons there have been 38 players(minimum 500 plate appearances) with an isolated slugging of at least .220. Howard is one of these players. With all of these sluggers, you'd expect massive strikeout rates, but as a group, they've struck out 20.0% of their plate appearances. While 20.0% is higher than normal, it's a far cry from Howard's 28.4%.
Compared to this group of "sluggers," Howard doesn't actually appear that good of one either. His .830 OPS is 8th worst in the group. His pitiful 1.5 fWAR is 2nd worst, ahead of just Mark Reynolds. Unfortunately he's paid as if he belongs at the top of this list with some of his firstbase peers in Miguel Cabrera, Prince Fielder, Joey Votto, and Albert Pujols. In case you aren't keeping track, the collective strikeout rate of that group is just 13.6%.
I'm not saying the sluggers nearing Howard's strikeout rate aren't good- just not among the very best.
So yes, sluggers do strikeout but the ones that don't tend to be more valuable players. It's a pretty simple concept that the more contact you make, the more chances the ball lands in the field(or over the fence) than in the catcher's glove.
Howard's salary suggests he's one of those elite sluggers but he's not thanks to those strikeouts, especially when given his position, lack of defense, and poor baserunning(which I'll delve into in a future post).