Why are people getting rid of their iPhone 5 from Sprint?

I've been looking on Craigslist and eBay for an iPhone 5 and most people are only selling iPhone 5 from Sprint. Is there something wrong with the service using that iPhone 5 or what?

Sprint sucks… Simple

Sprint is not that good as Verizon or AT&T so most people are disappointed with Sprint's mediocre service and 4G. That's why people are getting rid of their iPhone.