Managers don’t want singles. Statistical analysis has shown that swinging for the fences gets you more runs than trying to hit singles.
You could fix this by raising the walls, to make it harder to hit balls out of the park, thus changing the statistical advantage. Hitters would still get hits, sometimes doubles, by hitting off the wall, but doubles off the wall are not as valuable as home runs.
As of today, the three highest on-base percentages in the NL are .486 (Bellinger, LAD), .446 (Yelich, MIL), and .439 (McNeil, NYM).
Put all three of those on the same team and put them at the top of the lineup, and you'll find:
1. All other factors aside, the odds of the two batters reaching base safely in the same inning is only 21%.
2. The odds of ALL THREE of them reaching base consecutively is only 9.5%.
So even with the top three players in the National League in terms of on-base percentage, they are statistically likely to get on base consecutively fewer than once every two games.
Put three average players up in a row, and you'll probably find that it's maybe once every 4-5 games.
This is why teams rarely ever try to "manufacture" runs anymore.