That's a curious piece alright. What do you suppose caused such a granite block to crack like that? And I'm wondering why the other sections appear to be missing, but that lone segment remains. Also, not sure if it's an artifact of the photography, but the thing looks like it's tapered as if it's a piece of an obelisk.
It's not only blocks such as that one which are smashed, but even the basalt paving blocks as well.
It may be an obelisk but more likely a pillar.
The reason that everything is smashed is the logistics of transport. Although the AEs could transport massive blocks in one piece, those who recycled them couldn't. There is only so much load that a camel can bear before it gets back problems. If you were a camel, could you carry that remnant block down to Cairo, or wherever? Same reason for smashing off only the smooth faces on Bent Pyramid for example.