I think one problem is the dislocation streakiness produces in the lineup. If the guy puts up good numbers - goes to the top of the line-up, then crashes between the team's other high OBP hitters, he effectively spikes more rallies than if were batting 7th where his end of season numbers would have put him, or vice versa, the #7 hitter is suddenly hot and 5/6 don't gett on base and 8/9 don't drive him in so he ends up a LOB stat all the time. I don't have any math to prove it, but given that performance distribution in baseball is asymmetric around the mean and there is a strong non-linearizing BaBIP contraint on the upper limit, it just seems to me that consistent performance is going to allow for the best line-up optimization and thus the most runs through the season.