Why are these heat pumps so large?

Thats a shocker Steve, the average 2.5 ton outside coil that is installed down here has grown by around 25%, they used to be about 3 x 3 x 3 (27 cuft) to a newer 13 SEER at around 3.5 x 3.5 x 4 (around 40 cuft) I started noticing how big they were when inspecting units on condo roofs where you can find 40-50 of them of all ages.

Regards

Gerry