It would cause more problems than it would solve. If I wanted to transfer a char from Atlanta to Baja so that I could start playing on that shard and I had all the scrolls I needed on Atlantic to make two chars on the new shard as well, I wouldn't be able to do it. I could either sell my scrolls on Atlantic, transfer the gold, and hope I could find the scrolls to buy on the new shard, or make all the chars on Atlantic and then transfer them to the new shard, or just transfer the first char and do spawns on the new shard until I get the scrolls I need. Plus some people make their money by xshard trading items and scrolls.
Another thing would be if you couldn't transfer cursed items off a shard, then why would all these people that tranfer to farm them go to your shard? They normally transfer gold and buy things on your shard, create new chars, place houses, and add people doing things in Fel. Basically in the end the large shards would be real active as far as champ spawns goes, and the smaller shards would be pretty much dead because there wouldn't be enough people on the shard that would want to buy the scrolls that you did get.
...la
