time travel - In "Looper" was there a reason why they didn't send people directly to the furnace?

In "Looper" the future bad-guys send back people to be killed in a field by a guy with a stupid gun who then takes them into what appears to be a massively-insecure blast-furnace equipped factory of some sort.

Why couldn't they just make the people appear inside the furnace in the first place?

Was there a reason given other than it would have made for a considerably shorter film?