Ever wondered what happens to all those robot corpses that line the battlefield after a wave is over?
"Where do they go?", you ask, scratching your big bald head. Well fear not, you wonderful question-asker, you! (You're so good at asking questions, by the way. Everybody talks about how inquisitive and insightful they are - we host an annual convention about it. Got a ball pit and everything, whole nine yards.)

To answer your marvelous question (again, really great job), they get teleported away to a mysterious location hidden deep underground via little-understood and (likely) unstable ancient warlock magicks. A hive of socially maladjusted beatniks emerge from the walls and swarm around the pile of newly-summoned scrap in order to make... art. Which they sell. For money. I know, I'm as disgusted as you are.