"...In words that a four year old could understand please as it's pretty clear I'm just not getting this. Thanks in advance..."
This is how I see it mate, just my opinion.
Yesterdays game (as an example), second half, throw in from inside our half, Freeman has the ball, looking for options to throw to. Hanson shouts for the ball, two of their players get on on him, one in front and one behind, so he is sandwiched (calm down
LYDON 
) so that is not one man marking, he has taken two of their boys out of the game, Duffy or Coutts run in for the short throw, or alternatively, Freeman throws and Hanson has a go for it, with a decent success rate.
Set piece corner, Hanson moves to the back post, two (if not three) of their players follow him, creating space for others. Or, set piece corner, Hanson moves back to the edge of the box, ready to run in (whether he really means to or not), two or three of their players follow him, you can't give a big 6ft 4" lad room to run in and build up steam to head the ball in.
Hanson creates the space for Duffy, Fleck, Sharp, etc.
Hanson is not a flair player (like the excellent Carruthers), he is the height and physicality we have been missing to help make the chances, and chip in with some goals.
We would all love another "Billy Sharp", but there is only one.
Those cold afternoons, in seasons gone by, when we had no tall forward players, and had to watch the Oldham manager shout "Height!, Height!", to his lads, to reinforce the point that Scougall, Doyle, Baxter, Holt, etc, were no aerial threat no matter what, so just the kick the ball at about a six foot level and we would win nothing, are all gone and in the past.
What we really need, is the midfield player who bursts into the box (said it a lot recently) , because more often than not, we get the ball to Hanson, he has his back to their goal, he shields the ball from the opposition and plays the short, simple ball to the on rushing Duffy or Fleck, etc., and I want them to run into box from that point.
Sorry for the long winded answer, but the pacey, tricky player is Lavery, and he comes on after Hanson has given their defenders grief for 70+ minutes.
It's all about opinions of course, and at the end of the day, we are all Blades.