An extra base hit or a homerun is worth way more than a single, especially in shift situations (a defensive team is not going to shift to give up a single in a situation where a single is a big hit).
The difference comes in our perception that its a guaranteed single, which it isnt. You can still strikeout (in which case youve struck out trying to hit a worthless single instead of striking out trying to get an extra base hit), or hit a tapper, or pop it up, or fail in your bunt or whatever.
We think of the shift in terms of "Player X" always hits the ball to the right side, so lets shift to take that away. But its not really that, its also math, that if Player X tries and gets a meaningless single, we dont care, because it means he didnt hit a double or a homerun instead. The defensive team doesnt care about giving up that single all that much. The offensive team can do the same math too, and the reason they dont try for the single is because the conclusion after doing the analysis is the same one the defensive team came to. They dont care about getting that single just like the defensive team doesnt feel bad about giving it up. Trying for that single means giving up the chance at a bigger hit.