My research doesn't reveal the logic in most splits in a straight up single deck game.

Why would I double my investment on a proven losing split that I can't double? I have no chance of getting a blackjack. Now playing the hand "as is" could still win or losing your initial investment is worst case scenario. The consideration that seems to be overlooked is on the next hand for the same investment or adjusted I have the opportunity to get a blackjack or double down.

Splitting Aces and 99vs 4,5,6 88 vs 5,6,7 are worthy investments even without DAS. 77vs5,6 88vs4, and 99v7,8 are high value plays when the deck is rich in 10s and Aces. But the rest of the field are losing propositions for the most part. Logic is splitting may work out to breaking even on two hands as opposed to losing one. But this does not consider the next hand should one not split.

Again, most splits like 22,33,66 have very little affect on SCORE one way or the other.