I think the cross bunkers were strategic in that they forced the player to make a decision as to whether they could be carried to reach the green. Or perhaps a well-placed tee shot could allow the player to circumvent the cross bunker. It seems to me we think too much about "par" or reaching holes in regulation figures, while I think Ross designed holes with the understanding that some players might reach in two shots, while others might require three - or more! (The same strategy could also apply to long one-shot holes, where some players might require two shots to reach the green.)
The cross-bunkers made the second-shot more interesting for the moderate hitter who may be tempted to make the carry as well as for the very short hitter, who might need three full blows to get home. In a match play situation, the bold play might yield an advantage, but a failure to make the carry might lead your opponent to choose the more conservative play.
Without a cross bunker - or some other hazard short of the green - the second shot would be very uninteresting for the player who required three shots to reach the green. There are many Ross holes in New England in the 380-450 yard range with cross bunkers of some sort, where reaching the green in two shots would have been a challenge for many players. For many players, carrying those cross bunkers remains a challenge today.