I really, really doubt that enough of a whole planet's slave population consists of former nobles who suddenly decide that slavery isn't good enough for them.
Unlikely that the whole planet are former nobles, but they may still come from more comfortable conditions. A new slave from a wealthy consumer tech world is just as likely to be sent to work in the mines as a new slave from an agricultural world, the big difference: The one from the agricultural world is used to hard labour.
Citizens of a more luxurious society may not be expecting to work in harsh conditions, and may start to regret their decision when they get there.