Have a look at this simple position:
However, XG recommends 24/21 as the best move. Mine is fine, too (-0.05 worse). But still, why should I not put a builder on 11?
The answer is that the builder doesn’t help much – I already have the 5 point, 11 is too far away from the four point, and as my 8 point is stripped and my opponent has a stone on 2, building the 7 point in the next move with e.g. 11/7, 8/7 is not a great option. Also I underestimated that black has some really great rolls like 55 or 44. XG (on Roller++) also says that 13/10 would be slightly better than my move, because then the builder on 10 actually has something to build – the 4 point.
Similarly, black has made the 18 point, threatens to make the 20 point, so helping one checker to escape is reasonable, and a checker on 23 can’t jump past the 3-prime like a checker on 21 can. And on 21 we might start a good anchor.
Sometimes the straightforward move is not straightforward.